Office 365 Multiple Mailbox Migration
EdbMails Office 365 Migration Software lets you handle mailboxes as a single coordinated job rather than migrating them one at a time, in either direction: tenant-to-tenant, to on-premises Exchange, or to any other supported target. This page covers how EdbMails loads, maps, and concurrently migrates large mailbox sets: automatic and CSV-based bulk selection, mailbox mapping at scale, and parallel processing of up to 20 mailboxes simultaneously. For the full step-by-step migration process for your specific scenario, see the Office 365 to Office 365 guide, Office 365 to Exchange guide, or the full method comparison.
What is multiple mailbox migration?
EdbMails lets you select, map, and transfer many Office 365 mailboxes, including primary, shared, archive, and public folder mailboxes, within a single migration job, regardless of the target platform. Instead of configuring and running each mailbox as its own job, administrators load the full set at once, either manually or via CSV for tenants with more than 100 mailboxes, let EdbMails automatically map source mailboxes to target mailboxes, and run up to 20 mailboxes concurrently to cut total migration time in large environments. This capability applies across every EdbMails Office 365 migration scenario: tenant-to-tenant, Office 365 to Exchange, Office 365 to IMAP, and PST import or export. The migration path itself is covered in the scenario-specific guides above, or see all 5 migration methods for a full comparison; this page focuses on how EdbMails handles the mailbox set as a whole once that path is chosen.
Before You Start: Check Prerequisites for Multi-Mailbox Migration
Running a single mailbox and running twenty mailboxes concurrently both start from the same setup, but a few things matter more once you're loading a large batch at once.
1. Global Admin account
A Global Admin account with an active mailbox is required for Auto Registration of the EdbMails application on your Entra ID (Azure Active Directory). If you're using Manual Registration instead, either a Global Admin account or a user account with full access permissions will work.
2. Loading large mailbox lists
EdbMails automatically loads the first 100 mailboxes from a connected tenant. Due to a Microsoft-imposed limitation, tenants with more than 100 mailboxes cannot be enumerated directly beyond that count. For larger environments, load the mailbox list from a CSV file instead. The CSV method also gives you explicit control over exactly which mailboxes are included, which is useful even on smaller tenants when you want a curated scope rather than the full directory.
3. Bandwidth and throttling
Running multiple mailboxes in parallel increases the total bandwidth the migration draws at any one time. Microsoft applies throttling limits to Office 365 connections regardless of how many run concurrently, and EdbMails' automatic throttling management adjusts to these limits during the migration. Confirm your available bandwidth can support concurrent transfers before scheduling a large batch job.
4. Target-side setup
Prerequisites on the target server depend on where you're migrating to. See the prerequisites section of the Office 365 to Office 365 migration guide or the Office 365 to Exchange migration guide for target-side setup specific to your scenario.
Migrating Multiple Mailboxes: Step-by-Step process with EdbMails
This guide walks through migrating multiple Office 365 mailboxes in a single job using EdbMails. It covers loading a large mailbox list, mapping source and target mailboxes at scale, and running the batch concurrently, from initial setup through monitoring progress. For the full step-by-step process specific to your migration scenario, see the guides linked below.
Step 1: Install EdbMails and launch the application
- Download and install EdbMails software on your system.
- Click 'Login' or 'Start Your Free Trial' to get started.
- Check system requirements before running a large batch job, since bandwidth and system resources matter more once you're moving multiple mailboxes concurrently.
Step 2: Select your migration type
- Select the 'Office 365 Migration' option.
- Then choose the specific migration path you need (Office 365 to Office 365, Office 365 to Exchange, and so on).
- The bulk-handling steps below apply the same way regardless of which migration type you choose. Keep the default 'job name' or 'rename' it if you're running several batch jobs and want to tell them apart later.
- Select the 'Office 365 Migration' option.
Step 3: Connect to the source server and load the full mailbox list
- Click 'Add New Connection' to set up a new link to the source Office 365 account. To reuse an existing setup, choose it from the list and click 'Connect to Existing'.
- Choose the required connection options and click the 'Next' button.
- Select one of the secure OAuth 2.0-based modern authentication methods and authenticate on the Microsoft sign-in page.
- Click the 'Login' button to continue.
- After authentication, select a method to load mailboxes or use a CSV file to import them for migration.
- Select the multiple mailboxes you want to migrate from the source Office 365 server.
- Click 'Next' to proceed.
Step 4: Connect to the target Office 365 server
- Click 'Add New Connection' to connect to the target Office 365. To reuse a saved connection, select it from the list and click 'Connect to Existing'.
- Choose the desired connection options and click 'Next' to continue.
- Choose the appropriate target connection method and authenticate on the Microsoft sign-in page.
- Click the 'Login' button to continue.
- Choose one of the methods to load all mailboxes.
Step 5: Map source and target mailboxes
- Once mailboxes exist on the target server, EdbMails automatically maps mailboxes and folders between source and target based on display name, first/last name, and email address. With a large batch, review the mapping before proceeding and manually correct any mailboxes the automatic match didn't handle correctly, such as renamed users or mailboxes being consolidated.
- Once mailboxes exist on the target server, EdbMails automatically maps mailboxes and folders between source and target based on display name, first/last name, and email address. With a large batch, review the mapping before proceeding and manually correct any mailboxes the automatic match didn't handle correctly, such as renamed users or mailboxes being consolidated.
Step 6: Start multiple Office 365 mailboxes migration
- Click 'Start Migration' to begin the migration process.
- EdbMails processes the mailboxes concurrently rather than one after another by default, so the whole batch moves in parallel instead of queuing mailbox by mailbox. Click 'View Logs' at any point to check the migration report, and pause or resume the process as needed without losing progress already made.
Post-Migration Activities
Post-migration steps such as updating MX records, configuring Autodiscover, clearing Outlook's Auto-Complete list, and recreating Outlook profiles depend entirely on which target platform you migrated to. Follow the post-migration section on the guide that matches your scenario:
Benefits of EdbMails for Office 365 multiple mailbox migration
- Intuitive Office 365 migration interface
EdbMails provides a user-friendly software interface that allows you to complete the migration process in a few clicks, thanks to automation that automatically loads the mailbox from your Office 365 server and maps it between the source and target servers, saving time and manual work. You do not require any highly technical skills to perform the migration with the help of the software.
- Automatic mailbox loading from Source and target servers
EdbMails also provide a feature to load mailboxes automatically from your source and target servers. This feature will be particularly helpful to small organisations with 100 or fewer mailboxes, as it eliminates the need for manual effort. For larger numbers of mailboxes, it is possible to load mailboxes using the CSV method.
- Automatic handling of Office 365 throttling responses during migration
With Automatic Throttling management in EdbMails, there is no compromise with data migration between the Office 365 servers during peak and off-peak hours. This functionality removes manual waits and restart operations, which can be really helpful when you are moving a large number of mailboxes. This will avoid data loss and duplicity on the target server and thus save your effort and time during the migration process. Additionally, EdbMails helps prevent server hang-ups and ensures source mailboxes can remain accessible during supported data copy during migration.
- Optimised Performance and Speed
EdbMails enables concurrent mailbox migrations, thereby improving the speed of migration as the migration can occur for a larger number of mailboxes together. It allows performing 10 simultaneous migrations, but the limit of simultaneous migrations is raised to 20 mailboxes to achieve a higher speed of migration. Moreover, EdbMails can be installed on many machines and can migrate the distinct mailboxes to improve the speed of migration.
- Source mailbox access during data copy while Migrating to Office 365
EdbMails ensures Zero Downtime during your entire Office 365 migration, even during working hours. With the EdbMails migration process, the mailboxes will keep functioning without interruption. Mailboxes can continue to work from the source mailboxes till the time the entire mailbox is migrated. They can then resume working from the destination Office 365 tenant as soon as the migration is completed.
- Ensures Office 365 data Integrity during migration
While migrating to the target server, EdbMails will retain source mailbox data and ensure you with total migration of all mailbox elements, namely E-mails, attachments, calendars, contacts, etc. Hence, you can remain assured that nothing is lost/damaged during the migration.
- Securely migrates Office 365 mailbox data
EdbMails migrates your data using Microsoft's secure APIs and performs the migration according to Microsoft's prompted migration flow. The credentials you entered will not be saved on our servers, nor will your data. Your Office 365 credentials aren't saved and protected by OAuth 2.0 and TLS encryption during authentication. This software takes advantage of modern authentication method; MSAL (Microsoft Authentication Library and Microsoft Graph) & OAuth 2.0 are secure authentication methods for accessing your Microsoft Office 365 account.
- Support for all Office 365 Migration Methods
EdbMails supports all the possible Office 365 migration methods like cutover migration where entire mailboxes are being migrated all together or a staged migration, allowing migration for a batch of mailboxes. With the help of the above methods, an organization can opt for the method that suit their migration and need their requirements. Migrating few mailboxes or more number of mailboxes, EdbMails has an array of solutions to conduct successful Office 365 migration.
- Comprehensive Migration Reporting
The EdbMails provides a comprehensive Office 365 migration report for showing the in-depth analysis for the mailbox migration along with the mapping details. You can track the migration status of the every mailbox along with the count of the migrated folders and verify item counts, ensuring the integrity of the migration process.
- Cost-Effective Office 365 Migration solution
EdbMails offers an economical pricing plan to ensure your Office 365 migration can be implemented easily and without exceeding your budget. The system is on the basis of the count of source mailboxes which allows you to control your financial outflow. Our adaptable lifetime subscription plans allow for changes in the amount of users in correspondence with growth in business. Also, a 24/7 tech support and free software updates are provided with the software.
Frequently Asked Questions
How to perform Office 365 Multiple mailbox migration with EdbMails?
Step 1: Download and Install EdbMails software. Step 2: Select the 'Office 365 Migration' option. Step 3: Connect to Source Office 365 server. Step 4: Select multiple mailboxes for the migration. Step 5: Connect to target Office 365 server. Step 6: Select the required mapping option and start migration.
What are the benefits of multiple mailbox migration for Office 365?
There are several strong advantages in migrating multiple mailboxes to Office 365. One of the major advantages is faster mailbox migration efficiency where it allows the migration of multiple mailboxes simultaneously, thus drastically minimizing migration time. Users will be able to access their mails during migration with zero downtime.
This approach is highly scalable and flexible, and will fit organisations of any size. Administration becomes easier because of centralization of the migration management, streamlining administrative tasks.
Moreover, multiple mailbox migrations ensure the data consistency between the source and target environments and maintain data as source and target, along with the data integrity. This ultimately contributes to financial savings, increased operational agility, and a seamless and effective move to Office 365 and, by definition, can bring other benefits too.
Is there a limit to the number of mailboxes I can migrate?
EdbMails also facilitates the migration of bulk mailboxes at the same time, thus let you migrate data efficiently from Office 365 server. This means you can parallelly migrate 20 mailboxes by EdbMails which helps in performing the migration more effectively.
Though EdbMails allow you to migrate multiple mailboxes at once, but the actual numbers you can migrate depend upon number of mailbox licenses you own from EdbMails.
Click here to know the details of used and unused licenses from the EdbMails Office 365 migration window.
Does EdbMails provide reporting for migration status?
Yes, EdbMails includes granular reports on migration status, which details count of migrated items and source to destination mailbox mapping. While migration is being done, EdbMails will give you updates with the number of item transferred, ensuring you have a clear understanding of the data transfer.
While the migration is in process, EdbMails provides reports on the migration progress that show how many items were migrated.
Moreover, you can review the mapping between source and target mailboxes with EdbMails which ensures the data is migrated with right precision. With this reporting ability you can track the migration status in real time, allowing you to react if there are any problems to make it a successful migration experience.
Is EdbMails suitable for businesses of all sizes?
Yes, EdbMails can perfectly suit for the all types and sizes of businesses. EdbMails is versatile in nature and compatible with all small, medium, and large sized business environments. Whether you have loads of mailboxes to be managed or migration project requiring hundreds of users, EdbMails fits all your needs. The small business gains from its easy-to-use interface and cost-effective options, while the large business benefits from scale, the support for concurrent migrations, and powerful reporting capabilities.
What kind of support does EdbMails offer during migration?
EdbMails has complete support to carry out an Office 365 migration smoothly. The customer support executive is always present in 24x7 availability. They resolve issues and help out with migration needs. In addition, EdbMails provide many helpful resources, like documentation, instruction guide, email support, live chat support, tutorial, FAQ and knowledge base, all aimed at providing users with the detailed information and assistance.
