Office 365 to IMAP Migration

EdbMails provides a direct Office 365 to IMAP migration workflow for moving supported email data from Microsoft 365 / Exchange Online mailboxes to an IMAP-compatible destination. The source in this workflow is Office 365, and the destination is the IMAP server. EdbMails migrates supported messages, attachments, folders, and common message properties exposed by the source and accepted by the destination.

Direction note: This page covers Office 365 / Microsoft 365 → IMAP. If your source is an IMAP server and your destination is Microsoft 365, use the separate IMAP to Office 365 migration guide.

EdbMails Office 365 migration software can connect Microsoft 365 mailboxes to supported IMAP-compatible destinations such as Gmail, Zoho Mail, Zimbra, IceWarp, cPanel-hosted email, Plesk-hosted email, Rackspace Email, Dovecot, hMailServer, and other servers that provide compatible IMAP access.

The following sections guide you through the relevant Office 365 to IMAP migration scenarios, pre-migration tasks, migration steps, and useful tips required for migrating your mailbox data from Office 365 to various IMAP servers.

Organizations typically perform this migration when changing email providers, moving to a different hosted email service, or consolidating mailbox environments onto IMAP-based infrastructure. Standard IMAP migration covers email messages, attachments, folders, and supported message properties. Contacts, calendars, tasks, and other non-mail workloads require a separate supported method unless the destination also provides a compatible CalDAV/CardDAV workflow.

1. Office 365 to IMAP migration: Pre-migration tasks

   The following steps need to be completed before you can begin migrating your mailbox data from Office 365 to an IMAP server:

   Migration planning: before you start, identify the mailboxes to migrate, verify the destination IMAP settings, prepare the source-to-target mailbox mapping, and check mailbox sizes against the destination. See the Office 365 to IMAP Migration Checklist below for the full before, during and after list.

   • On the source Office 365 server side:
     1. Use the Microsoft 365 account, application registration, and permissions required by the EdbMails connection method you select. Use Global Administrator privileges only where that connection or tenant-consent workflow requires them.
     2. Assign the suitable Office 365 licenses for the required mailboxes

         Click here to assign Microsoft 365 licenses to user accounts

     3. To migrate your Office 365 public folders and archive/shared mailboxes you must set them up correctly.

         Click here to create Office 365 Public folder and assign admin permissions.

         Click here to create Shared mailboxes on Office 365 and set the required permission.

         Click here to enable archive mailboxes on Office 365

     4. Make sure that you have the required Bandwidth for Office 365 migration

         Click here for network and migration planning, performance factors and best practices for Office 365 migration.

     5. Review large-message and mailbox limits on the destination IMAP service before migration. Messages that exceed the target provider's accepted size or quota may require separate handling.
   • On the target IMAP server side:
     1. Get your IMAP server host name, port number, email address, and password to log in to the target IMAP server.
     2. If migrating multiple mailboxes, prepare a CSV file with columns as email address, password, IMAP server host name, and port number.
     3. If Gmail is the target, use the Google authentication method supported by the selected EdbMails connection. Google recommends Sign in with Google where supported; an app password should be used only when the workflow requires it and the Google account is eligible for app passwords.

         See the Gmail app-password guidance.

2. Selective Office 365 to IMAP Migration

   Selective migration allows administrators to migrate only the required Office 365 mailboxes to an IMAP destination instead of moving the complete environment. This approach is useful for phased migrations, or when only specific users or departments need to be transferred while the rest remain on Office 365.

3. How to Migrate Office 365 to IMAP Using EdbMails

   EdbMails can help you with a smooth and simple migration from Office 365 to IMAP with a user-friendly interface. So you can migrate all your mailboxes' data easily and securely with the following steps:

   Step 1: Download and Install EdbMails application

   • Download and install the EdbMails application on your computer.
   • Double click the EdbMails setup (EdbMailsSetup.exe) to install the application.
   • Follow the instructions that appear to complete the installation.

      See EdbMails system requirements for Office 365 migration

     

   • Click 'Login' or 'Start Your Free Trial' to access the application

     

   Step 2: Select Office 365 to IMAP Migration option

   • Select the option 'Office 365 Migration'

     

   • Select ‘Office 365 to IMAP migration’

     

   • Either keep the default job name or enter your preferred job name, then click 'Next' to proceed.

     

   Step 3: Connect to source Office 365 server

   • Click the ‘Add New Connection’ button to establish a new connection to the source Office 365. To use the previous connection, select it from the connection list and click the ‘Connect to Existing’ button to proceed.

     

   • Choose the required connection options and click the ‘Next’ button.

     

   • Select the appropriate connection method and click the ‘Login’ button to continue.

     

       Connect to Office 365 server using secure modern authentication

   • Authenticate on Microsoft sign-in page.

     

      After the successful authentication, choose one of the methods to load the mailboxes. You can also load and migrate the mailboxes using a CSV file.

     

   • Select the mailboxes you want to migrate from the source Office 365 server.
   • Click ‘Next’ to proceed.

     

   Step 4: Connect to target IMAP server

   • For this Office 365-to-IMAP workflow, choose 'Connect to IMAP'. To connect a single target account, select 'Single User / Account Migration.'

     

   • Select the appropriate IMAP host name from the list or enter it manually, then provide the target mailbox address and the authentication credential required by that provider. For Gmail, use the Google authentication method supported by the selected EdbMails connection; use an app password only when required and available for the account.
   • Click the ‘Login’ button.

     

   • Once the mailboxes are loaded, click ‘Next’ to proceed.

     

   • For migrating multiple mailboxes, choose 'Multiple (Bulk) Users/Accounts Migration,' and click 'Next' to proceed

     

   • Click on ‘IMAP Migration CSV File.’
   • You will be prompted to download the sample .csv file. Choose the destination folder where you want to save the file

     

   • Open the downloaded CSV file and update it with the required details, including the email address (mailbox name), password, host name, and port. You can set other fields to 'NA' as they are not required when migrating email data. After making the changes, save and close the CSV file.

     

   • Click the 'Load Modified CSV File' button to select the CSV file.
   • Verify the mailboxes and proceed by clicking 'Next'.

     

   • To migrate calendars and contacts, along with emails, from Office 365 to an IMAP platform that supports CalDAV/CardDAV, select ‘IMAP with CalDAV/CardDAV Migration CSV File’.

     

   • You will be prompted to download a sample CSV file, choose a location on your computer, and save it.
   • Open the CSV file and update it with the required details: Source Mailbox Name, Password, Host, Port, CalDAV Username, CalDAV Password, CalDAV Server, CalDAV Folder, CardDAV Username, CardDAV Password, CardDAV Server, CardDAV Folder. Save and close the CSV file.

     

   • Click on ‘Load Modified CSV File’ and browse to the location where you saved the updated CSV file. Select the modified CSV file and load it into the application.

   Step 5: Start Office 365 to IMAP migration operation

   • After mapping the mailboxes, click the ‘Start Migration’ button and initiate the migration process.

     

   • To review the migration report, click the ‘View Log’ button, which provides a comprehensive report detailing the number of emails, folders, and mailbox items successfully migrated.

     

   • Also, log in to your target server and verify the migrated items.

4. Post migration actions for Microsoft 365 to IMAP

   If the target IMAP service will become the production mail host for your custom domain, update the required MX and related DNS records only after validating target mailboxes and mail flow. If the migration is only copying historical mail or the domain's production routing is not changing, an MX change is not required.

5. Office 365 to IMAP Migration Checklist

   Before migration:

   • Verify Office 365 access and admin permissions.
   • Confirm the IMAP server details for the destination.
   • Create the required mailboxes on the destination server.
   • Prepare the source-to-target mailbox mapping.

   During migration:

   • Monitor migration progress.
   • Review the migration reports.
   • Check migration status for each batch.

   After migration:

   • Verify mailbox access on the destination server.
   • Confirm the migrated email folders.
   • Validate the migrated messages against the migration report.

6. Best Practices for Microsoft 365 to IMAP Migration

   There are several recommended best practices for migrating your Office 365 to an IMAP account. These practices help make the process of moving a mailbox to an IMAP account smooth and predictable.

   1. Start the migration planning process early: Begin the migration planning process well in advance to prevent possible migration challenges.
   2. Select a reliable migration solution: Choose a migration tool that supports secure authentication, mailbox filtering, incremental migration, and detailed reporting to help ensure a smooth Office 365 to IMAP migration process.
   3. Batch the migration: You can better manage the migration by breaking it down into batches. This will make troubleshooting and managing the migration easier.
   4. Conduct a pilot migration: Test a small set of mailboxes before the full migration to identify and resolve potential issues.
   5. Ensure transparent communication with stakeholders: Communicate consistently and openly with all stakeholders involved. Make sure all stakeholders are aware, follow their deadlines, and understand what they need to do.
   6. Monitor migration progress: Continuously monitor migration activity, logs, and reports to ensure the migration proceeds as expected.
   7. Optimize migration performance: Run multiple mailbox migrations concurrently based on Microsoft 365 limits, destination-server limits, available bandwidth, and migration-computer resources.
   8. Use multiple migration workstations when required: Running migrations from multiple systems can help distribute workload and reduce overall migration time.
   9. Use incremental migration: Incremental migration transfers only new or previously unmigrated items during subsequent migration runs and helps prevent duplicate data on the destination server.

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Additional resources:

• Office 365 migration software
• Office 365 to Zimbra migration
• Office 365 migration filter settings
• Office 365 migration reports
• Reverse direction: IMAP to Office 365 migration