Exchange to Office 365 migration

Exchange server vs Office 365

Discover the enhanced capabilities of Office 365 compared to Exchange server. Enjoy advanced features such as Email Archiving, Retention Policies, Encryption, Backup and Recovery, Auditing and Reporting, Mobility, and convenient Email access from multiple devices and the web. Explore the comprehensive table below to see the key differences between Exchange and Office 365.

Explore the versatility of Exchange Online, an integral part of Office 365. Easily transition to a standalone Exchange Online plan or delve into the extensive productivity suite offered by Office 365. Prior to migrating from Exchange server to Office 365, it is vital to understand  Microsoft 365 suite features and carefully choose the license plan that suits your requirements.

 In this guide, we describe the pre-migration activities, the different migration paths from Exchange to Office 365 and the post migration activities.

What is the best way to migrate from Exchange server to Office 365?

EdbMails Exchange to Office 365 migration tool is the perfect solution to simplify the process of migrating Exchange server mailboxes to Microsoft 365. It securely moves mailboxes with emails, contacts, tasks, journals, appointments, calendars, and notes from the source to the target with complete data consistency. The tool supports the migration of multiple user mailboxes, private and public folders, shared and archive mailboxes. With its user-friendly interface, EdbMails makes mailbox migrations to the cloud fast and easy, eliminating the need for PowerShell scripts or extensive technical knowledge.

1. Exchange to Office 365 Migration Checklist

   Moving to Office 365 from Exchange can be challenging if you have a large number of mailboxes and data to migrate. The following points can help you safely transfer all your mail data to the cloud without a hassle.

   1. Plan for the migration:
      • Identify the scope of the migration, including the number of mailboxes, public folders, and other data that needs to be migrated.
      • Determine the size of the mailbox data and number of mailboxes to migrate.
      • Assess the current environment, including hardware, software, and network configurations.
      • Prepare a complete inventory of items that you want to migrate.
      • Determine the migration schedule, including the timing and duration of the migration.
      • Identify any specific requirements or constraints that may affect the migration.
      • Communicate any changes to your end users and inform the stakeholders.
   2. Prepare the data for migration:
      • Perform a full Exchange server backup and all related data.
      • Clean up and archive any unnecessary data to reduce the amount of data that needs to be migrated.
      • Perform a test (pilot) migration to identify and resolve any issues before the full migration.
   3. Purchase and configure Office 365 licenses:
      • Purchase the necessary Office 365 licenses for all users that will be migrated.
      • Configure the Office 365 tenant, including creating and configuring users, mailboxes, public folders and other resources.
   4. Configure the domains and DNS records:
      • Prepare the domains and required Active Directory services on the target.
      • Update the DNS records to point to the Office 365 tenant, including MX records and Autodiscover.
      • Verify that the DNS changes have propagated and that email is flowing to the Office 365 tenant.
   5. Perform Exchange to Office 365 migration with EdbMails:
      • EdbMails can help you with Exchange migrations to the cloud
      • Configure the migration settings and migrate mailboxes, Public folder and Shared mailboxes.
      • Monitor the migration progress and verify the migrated items
   6. Test and validate the migration:
      • Test the migration by sending and receiving email and verifying that all data has been migrated correctly.
      • Validate the migration by checking for any missing data or issues, and troubleshoot as needed.
      • Perform a final backup of the Exchange server before decommissioning it.
   7. Post-migration tasks:
      • Update email client settings, such as Outlook, to point to the Office 365 tenant.
      • Create new Outlook profiles and check if you are receiving mails correctly.
      • Update any custom scripts or applications that access the email data to point to the Office 365 tenant.
      • Update any third-party services or integrations that access the email data to point to the Office 365 tenant.
      • Update the helpdesk and end-user documentation to reflect the new email environment.
      • Train users on the new email environment and any new features or functionality provided by Office 365.
      • Decommission the source Exchange server if you no longer plan to use it (optional).
   8. Monitor and maintain:
      • Monitor the Office 365 environment for any issues or performance problems.
      • Maintain and update the Office 365 environment as needed.
      • Continuously review and improve security, backup, and disaster recovery strategies.

2. Exchange to Office 365 Migration Planning

   • Step 1: Decide on a suitable Exchange to Microsoft 365 migration type

     The first step is to plan the Exchange mailbox migration to Office 365. Depending on your source and target environments, the following migration paths are available.

     Migration Requirement	Ideal migration approach	Migration flow
     You want to move all of your email, calendar, and contacts from Exchange to Office 365 at once.	Exchange cutover migration	Set up your target Office 365 tenant and migrate everything to the cloud all at once. Suitable for large-scale mailbox migrations
     You prefer to transfer mailboxes from Exchange Server to Office 365 in smaller batches or on weekends.	Staged Exchange migration	Migrate your mailboxes and mail data in stages, transferring the most recent data first, followed by the others.
     You want to retain your on-premises Exchange server and prefer moving to Office 365 gradually	Hybrid migration	Move mailboxes to Office 365 in a Hybrid deployment of Exchange and Office 365.
     You want to migrate from a legacy Exchange such as 2003, 2007 or 2010 to Office 365 or when you do not have access to your Exchange server.	EDB or IMAP migration method	Migrate mailboxes with an EDB file or by using an IMAP connection.

      Use the Microsoft 365 mail migration advisor to determine which migration method is best for you.

   • Step 2: Install cumulative updates (CU) on the Exchange server

     Ensure that you have the latest updates installed on the source Exchange.

     1. Install CU for Exchange server 2010
     2. Install CU for Exchange server 2013
     3. Install CU for Exchange server 2016
     4. Install CU for Exchange server 2019
   • Step 3: Consider the network and bandwidth requirements
     1. Network requirements
        1. Understand the networking roadmap for Microsoft 365. It involves planning, deploying and managing your network.
        2. Internet Connectivity: A stable and reliable internet connection is required for migration of Exchange to Office 365. The internet connection should have sufficient bandwidth to handle the data transfer and should be free from congestion.
        3. Firewall and Port Configuration: Review and configure the firewall and port configurations to allow for the necessary data transfer to the Office 365 tenant.
        4. DNS Configuration: Review the DNS records and configure them to point to the Office 365 tenant, including MX records and Autodiscover. This task ensures that email is properly routed to the Office 365 tenant after the migration.
        5. Network Latency: Consider the Network Latency to ensure a seamless data transfer. If the Network Latency is high, it may slow down the migration process. See how Microsoft 365 networking is different.
        6. Office 365 Throttling: Microsoft limits the number of concurrent mailbox transfers to ensure service availability. Consider the Office 365 throttling policies when you migrate large mailboxes.
        7. Network Security: Review the network security to ensure that the data transfer is secure. This includes configuring any necessary encryption, authentication, and access controls.
        8. Network Load Balancing: Consider the Network Load Balancing to ensure that the data transfer is balanced across multiple networks and to avoid any bottlenecks.
     2. Bandwidth requirements

        Bandwidth requirements for Exchange to Office 365 migration can vary depending on several factors, such as the number of mailboxes, the amount of data to be migrated, and the migration method used. Use tools like Microsoft Remote Connectivity Analyzer and connectivity test tool to test your existing network.

        1. Number of mailboxes: The number of mailboxes being migrated influences the overall bandwidth requirements. The more mailboxes you plan to migrate, the more bandwidth you will need. See bandwidth requirements for Office 365 migration.
        2. Mailbox Size: The size of the mailboxes being migrated also influences the overall bandwidth requirements. Larger mailboxes will require more bandwidth to migrate.
        3. Migration Type: The type of migration you use also affects the bandwidth requirements. For example, a cutover migration, where all mailboxes are migrated at once, requires more bandwidth than a staged migration, where mailboxes are migrated in smaller groups.
        4. Migration schedule: The schedule of the migration also influences the bandwidth requirements. For example, migrating during off-hours or over a weekend when network traffic is typically lower, reduces the overall bandwidth requirements.
        5. Network infrastructure:. A network with higher bandwidth capacity can handle more data during the migration.
        6. Network Latency: Network Latency between the source and destination servers is also a factor to consider during the migration. If the Network Latency is high then a higher bandwidth is required.

      See best practices for network planning and improving migration performance.

     Note: If you have already configured your Office 365 tenant, you can directly skip to Step 7 in this section.

   • Step 4: Select a suitable Microsoft 365 license plan that fits your needs

     Microsoft 365 is available as a cloud-based subscription service and offers a variety of licensing options, each tailored to a specific user needs. It is recommended that you thoroughly evaluate the Office 365 business plans and Office 365 enterprise plans to determine which one best meets the needs of your organization. You can also sign up for a 30-day free trial of Office 365 to test out the various plans before making a final decision.

   • Step 5: Set up your target Office 365 Tenant for the migration
     1. Create an Office 365 Tenant: Plan for the Tenant implementation and deploy the tenant. See the tenant roadmap for Office 365.
     2. Sign in to the Microsoft 365 admin center: Microsoft 365 admin center (https://admin.microsoft.com/) and sign in with your global administrator credentials.
     3. Customize the Tenant settings: After the tenant is set up, configure and customize the settings such as email domains, language, and time zone to suit your organization's needs.
     4. Configure Azure AD Connect: Azure AD Connect is used to synchronize your on-premises Active Directory with Azure AD. This step is necessary if you want to retain your on-premises in a Hybrid environment and to enable single sign-on (SSO) for your users.
     5. Configure email clients and apps: If you want to install Office 365 apps and Outlook, see system requirements for Microsoft 365 and Office configuration support matrix. Because Office 365 is a cloud based solution, it is also important to learn where your Microsoft 365 customer data is stored.
     6. Set up Office 365 services: Besides email, you may want to set up additional services such as SharePoint, OneDrive and Teams.
     7. Establish data retention policies: With Office 365, you have the ability to retain data in accordance with compliance and legal requirements. Set up data retention policies to meet your organization's compliance needs, and if necessary configure retention policies for specific mailboxes or groups of users
   • Step 6: Add and verify the custom domain on Office 365

     If you have a custom email domain from your hosting provider to which you want to migrate and receive emails, you must add and verify the domain on Office 365. This will enable you to use your own domain name (such as example.com) for your email addresses and other Office 365 services.

      To set up your custom domain, follow these steps:

     1. Verify that you own the domain by adding a TXT record to your DNS configuration.
     2. Add a new domain to your Office 365 tenant. You can use an existing domain that you own or purchase a new one. The domain is used to access your Office 365 services. 
     3. Update your DNS records to point to Office 365. This step is required to ensure that your email is delivered to the correct mailbox. You can also update the MX records after you complete the migration.
   • Step 7: Create mailboxes and set up mail-enabled Public folders

     Before you migrate to Office 365, ensure that you create mailboxes for users in your organization and assign suitable licenses to them.

     1. Add users and assign licenses to Office 365 users
     2. Add several users at the same time to Office 365
     3. Assign Microsoft 365 licenses to user accounts

     If you want to migrate Exchange public folders to Office 365 , then create and configure Public folders and make them mail enabled on Office 365.

     1. Create Office 365 Public folder and assign mailbox user
     2. Enable In-Place Archive mailboxes in Office 365
   • Step 8: Set the impersonation role to the admin user on the source

     Ensure that you set the following permissions to the admin account on the source and target server and that the mailboxes you migrate are not hidden from the address lists.

     1. On the source
        1. ApplicationImpersonation
        2. View-Only Configuration - Run the cmdlet New-ManagementRoleAssignment using the Exchange Management Shell to assign the View-Only Configuration role to the admin.

            Click here to set the impersonation rights in Exchange server using powershell for Exchange 2019, 2016, 2013, 2010

            Click here to set the impersonation rights in Exchange server using powershell for Exchange 2007

     2. On the target
        1. ApplicationImpersonation

     Setting impersonation rights in Office 365 is a simple process that can be done quickly using the Admin Center. Assigning the Organization Management role group to the admin user in Exchange Online is an elevated permission that is required to migrate public folders. However, with EdbMails, this step is automated, as the tool automatically sets the necessary impersonation rights, saving you time and effort during the migration process.

      Click here to set the impersonation rights in Office 365 using powershell

   • Step 9: Verify the mailbox of the admin account

     Check to see if the admin account that has been assigned management roles has a valid and non-hidden mailbox on the Exchange 2016 server. See how to configure user mailbox properties for the users from the Exchange admin center (EAC).

   • Step 10: Configure Office 365 to send and receive large messages

     Increase the message size limit on Office 365 to 150 MB. This option enables you to bypass message size limitations during the migration.

3. Exchange to Office 365 Migration using EdbMails

   The following methods help you perform Exchange to Office 365 mailbox migration with EdbMails migration tool.

   • Method 1: Cutover Exchange server to Office 365 migration

     • Step 1: Download and install EdbMails Exchange migration tool
       • Download EdbMails and install the application on the source computer. You can also perform the migration operation by installing EdbMails on any Windows computer connected to your source On-Premises Exchange server.
       • Launch the application and click ‘Login’ or ‘Start Your Free Trial’.

         

       • Select the migration option as 'Live Exchange migration'.

        See the detailed list of EdbMails system requirements for Exchange migration.

       

       Note: If the Standard folders (such as Inbox, Calendar, and Contacts) on your source Exchange server mailboxes are set to a different language, follow the instructions in the link to migrate these folders to the respective system folders on the target (destination) server.

       For instance: If your source Inbox folder is named 'Boîte de réception', which is in French language and you migrate this folder directly to the destination server, then by default it will not be mapped to the 'Inbox' folder on the target server. In order to map the folder with the french name to the respective folder, change the language settings on the target server to match that of your source mailbox folder (in this case, it is French).

     • Step 2: Select the option to connect to Exchange server

       Before migrating, create a customized throttling policy to prevent any potential performance issues with your Exchange server. In the ‘Connect to Exchange Server (Source)’ window, you have the option to choose among ‘Connect using Global Admin User’, ‘Connect to Specific User’,  or ‘Connect to Hosted Exchange Server.’ Select the appropriate option based on your requirements and configuration.

       With EdbMails, you can migrate mailboxes, public folders, and archive mailboxes from the source Exchange to the target server. See how to use the different Exchange server connection methods supported by EdbMails.

       

       After logging into source Exchange server, select an option to load the mailboxes. EdbMails automatically loads your source mailboxes. You can also load the mailboxes using a CSV file.

     • Step 3: Select the mailbox items and connect to target Office 365

       EdbMails displays a list of mailboxes from the source Exchange server.

       • Select the mailboxes and folders that you want to migrate to Office 365

          Tip: If this is the first time you’re migrating with EdbMails, the migration is a full migration. On subsequent migrations from the same source to the target, the migration is incremental. The incremental transfer ensures that only the new and updated items are migrated to the target without creating duplicates.

       • Click 'Migrate to Office 365' to set up the connection with the target server

         

     • Step 4: Log in to Office 365 tenant as Global Administrator

       EdbMails supports a modern authentication method to connect to your Office 365 . Connect to the target server by selecting ‘Auto’ or ‘Manual’ registration and the connection method among Mailboxes, Public folder or Archive Mailbox.

       EdbMails is a highly secure application and uses TLS encryption along with OAuth 2.0 authentication for login. It does not store your user credentials. Learn how to connect to Office 365 server with modern authentication.

       

        Tip: The mapping activity in EdbMails can automatically match and map the mailboxes and folders between the source Exchange server and the target Office 365. This activity saves time when you’re migrating a large number of mailboxes.

     • Step 5: Migrate the Exchange mailbox account to Office 365

       Start and monitor the migration after you complete the mailbox mapping. Finally, verify the count of migrated emails, folders and mailbox items with EdbMails text-based log report.

       

   • Method 2: Microsoft Exchange to Office 365 staged migration

     EdbMails supports staged migration to Office 365 from all On-Premises Exchange servers, including 2007, 2010, 2013, 2016 and 2019. You can select specific mailboxes, apply the various filter conditions to migrate the mailboxes, emails and items in batches.

     • Step 1: Install EdbMails and select Live Exchange migration

       From the application main window, select the ‘Live Exchange migration (Hosetd, hybrid, on-premise & more…) ’ option as shown in the screenshot below.

       

     • Step 2: Connect to the source Exchange server

       In the connect to Exchange server window, select the required connection option among 'Connect using Global Admin User’, 'Connect to Specific User’, ‘Connect to Hosted Exchange Server’.

       Once you log into the source Exchange server, you have the option to load the mailboxes. EdbMails conveniently loads your source On-Premises mailboxes automatically, saving you time and effort. Alternatively, you can also choose to load the mailboxes using a CSV file, providing flexibility in the migration process.

       If you have a large number of users, you can use directory synchronization to create users in Microsoft 365.

       

     • Step 3: Select the mailboxes and apply folder and mail filters

       After you load the CSV file, EdbMails displays all the mailboxes. You can perform staged migration to Office 365 based on the Date and other conditions with the following options.

       1. Additional Include and Exclude Filter Options
       2. Remove deleted source items from target folders.
       3. Filter emails by Date: Migrate all emails between two specific dates.
       4. Filter emails by Size: Exclude emails from migration larger than a specified size.
       5. Filter emails by Domain: You can filter all emails by the sender domain and migrate them to Office 365.

       By applying the folder options, you can exclude the Standard/Custom folders such as Junk, Conversation History, Drafts and others.

       

     • Step 4: Start the Exchange on-premises to Office 365 staged migration

       Apply a label to the migration task to save the settings for future migrations. Finally, match the mailboxes between the source and target and start the migration. After the operation is complete, verify the same with the log report. You can create a new migration batch with the CSV file to migrate mailboxes of the other users.

   • Method 3: Exchange to Office 365 Hybrid migration

     In the Hybrid migration scenario, both Exchange on-premises and Exchange online coexist in the same Active Directory environment. For example, the hybrid deployment enables you to use a global address list (GAL) with a centralized mail flow.

     Hybrid migration prerequisites

      Make yourself familiar with the Exchange server Hybrid deployment. Learn more about the Hybrid deployment features and the Exchange hybrid components. Consider the following points and ensure that you have the required bandwidth for the migration.

     • Ensure that you meet the Hybrid deployment prerequisites
     • Install the latest version of the Exchange Server cumulative update on your on-premise servers.
     • Update any Edge Transport servers to the latest CU.
     • Register any custom domains you want to use in the Hybrid with Office 365.

     Steps for Exchange Hybrid migration to Office 365

     • Step 1: Set up your environment for Hybrid deployment
       1. Confirm that your environment meets the necessary requirements for a hybrid migration.
       2. Ensure stable network connection between on-premises Exchange server and Office 365
       3. Add your existing domain on Office 365 and verify it with a TXT record.
       4. Install Hybrid Configuration Wizard (HCW)
       5. Run the wizard and configure the necessary settings
     • Step 2: Set up Directory synchronization for Microsoft 365

       In order to synchronize your on-premises Active Directory with Azure Active Directory in the hybrid deployment, you have to configure directory synchronization with the Azure AD Connect tool.

       1. Install Azure AD Connect tool
       2. Run the tool and configure the necessary settings
     • Step 3: Perform Hybrid Exchange migration with EdbMails
       1. Use EdbMails to migrate Hybrid Exchange to Office 365.
       2. Your Public folders cannot exist on Office 365 and on-premises Exchange at the same time. See a workaround solution for Exchange hybrid public folder migration.
     • Step 4: Monitor and complete the migration to Office 365
       1. Verify the migration with EdbMails log report
       2. Configure the email routing by adding MX records
       3. Decommission your on-premise Exchange server if you no longer require it.

   • Method 4: Migrate email from Exchange to Office 365 with IMAP

     This migration type is useful and appropriate in the following scenarios:

     1. When you have a small number of mailboxes to migrate.
     2. When you want to migrate from older versions of Exchange such as 2010.
     3. When your email system such as Hosted Exchange supports IMAP.
     • Step 1: Download EdbMails and select IMAP migration

       After you launch the application, select the 'IMAP migration option' from the main window.

       

     • Step 2: Connect to your Exchange server with IMAP

       Before you migrate, create a CSV file with a list of user mailboxes. Fill out the IMAP server details in the sheet and select 'Multiple (bulk) Users/Accounts Migration' as shown. Choose IMAP as the connection method and load the mailbox names from the CSV file.

       

     • Step 3: Select the mailboxes and connect to the target server

       EdbMails connects to and lists all your mailboxes. Select the mailboxes and click 'Migrate to Office 365' to connect to the target server.

       

     • Step 4: Map and migrate the Exchange users to Office 365

       The application can also map and match the mailboxes between the source and the target server. Verify the mapping details and migrate all your emails to Office 365. Log in to your target server and check if the migrated items are present.

     • Step 5: Migrate Contacts and Calendars from Exchange to O365

       The IMAP migration only migrates emails; to migrate your calendars and contacts, export them to a flat file such as CSV or iCal format, and then import them into your Office 365 account.

        Learn how to import calendars and contacts into Microsoft Office 365.

   • Method 5: Exchange server migration to Office 365 with EDB file

     If your Exchange server has crashed or is no longer accessible, then you can migrate the on-premise Exchange to Office 365 by using the EDB file. EdbMails can help you migrate mailboxes from Exchange 2003, 2007 and 2010. It can also recover EDB from Dirty Shutdown errors and convert the EDB to PST format.

     • Step 1: Install EdbMails tool for EDB to Office 365 migration

       After you install and launch the application, select the ‘EDB to PST. EDB to Office 365. EDB to Exchange. EDB Public Folder’ option in the main window. This method enables you to easily migrate from an inaccessible Exchange to the cloud in a few clicks.

     • Step 2: Browse and select the offline Exchange EDB file

       Take a copy of the EDB file as a backup and select the Exchange EDB file from your computer. The application can recover STM, Pub.edb, priv.edb and mailbox databases from old and legacy Exchange servers.

       

     • Step 3: Select the Exchange mailboxes and click ‘Migrate to Office 365’

       After the recovery operation, you can preview all the emails, mail items and even recover deleted emails. Select the required mailboxes, folders and connect to the target server.

       

     • Step 4: Switch from Exchange to Office 365. That’s it!

       After you sign in to your Office 365 tenant, select the required option to migrate mailboxes or public folders and proceed to the mapping options. Start the Exchange mailbox migration to Office 365.

   • Method 6: Migrate Microsoft Exchange to Office 365 with PST files

     If you have your Exchange mailboxes exported as PST files or if you want to transfer mailboxes from a backup PST file to Office 365, then this method is the most suitable approach. With EdbMails you do not have to manually upload your mailbox data unlike the Microsoft PST upload method. The application automatically connects to your target server and enables you to easily move from Exchange to Office 365.

     • Step 1: Select PST to Office 365 migration in EdbMails

       Launch EdbMails and select Office 365 migration on the main screen. Close the source connection window and select the PST migration option.

       

     • Step 2: Add multiple Outlook PST files that you want to migrate

       Select and bulk-add the PST files containing Exchange mailboxes. Follow the steps 1-3 as shown. Using the PST migration method, you can also migrate contacts and calendars to Office 365.

     • Step 3: Convert on-premise Exchange mailboxes to Office 365

       Connect to the target Office 365 server and map the mailboxes and folders. Start the mailbox migration and verify if all of your mailbox data is present in the target.

4. Exchange to 365 Post Migration Tasks

   • Step 1: Verify that all mailboxes have been successfully migrated

     One of the most important steps after migrating is to ensure that all your Exchange mailboxes have been moved to Office 365. You can use the log report from EdbMails or log in to your account and verify the mailbox items.

   • Step 2: Update the DNS (MX) records to point to Office 365

     If you haven’t added the DNS records, you must add and update the MX records to enable your email to work with the target server and receive messages on Office 365. In addition, configure the Autodiscover record to allow Outlook to connect to the migrated mailboxes.

   • Step 3: Create a new Outlook profile and update the client settings
     • Ensure you have the latest version of Outlook installed to avoid compatibility issues.
     • Configure the Outlook profile for each user in your domain if Outlook has problems connecting to Office 365 mailboxes.
     • Configure the new server settings, such as the server address, username, and password in Outlook.
     • Test email flow to ensure that your users are able to send and receive emails.
   • Step 4: Uninstall and decommission the source Exchange

     The following points provide an overview of the steps to decommission on-premise Exchange server.

     • Verify that all mailboxes have been successfully migrated to Office 365. Check the status in the Exchange admin center or with the PowerShell Get-MailboxStatistics cmdlet.
     • Make sure that all Outlook clients are configured to connect to Office 365. You can use the Test-OutlookWebServices cmdlet to check the connectivity of Outlook clients.
     • Perform a final Exchange server backup before decommissioning it.
     • Disable all mail flow on the Exchange server by removing the Receive Connector or disabling the SMTP service.
     • Ensure that all public folders have been migrated to Office 365. You can use the Get-PublicFolder cmdlet to check the status of public folders.
     • Uninstall the Exchange server software from the Control Panel.
     • Remove any remaining Exchange-related hardware or virtual machines.
     • Verify that no mailboxes or public folders remain on the Exchange server.
     • Finally, remove the server from the Active Directory and DNS.
     • Once you verify that everything is working fine, you can decommission your on-premises server.
       1. Steps to decommission Exchange 2013
       2. Steps to decommission Exchange 2010
       3. Modify or Remove Exchange 2010
       4. Remove Exchange 2007 organization
       5. Uninstall Exchange Server 2003
       6. Decommission Exchange server in a Hybrid deployment

Exchange migration troubleshooting

 See the troubleshooting solutions for Exchange and Office 365 migration. For more information related to EdbMails Exchange migration, see frequently asked questions.