How to migrate IMAP mailboxes to Microsoft 365?

When you deploy Microsoft 365 in your organization, you can migrate data from your IMAP Server accounts to Microsoft 365. We would like to help users in such a migration by explaining the steps to migrate IMAP mailboxes to Microsoft 365. See the methods and steps for performing the migration systematically.

Migrate IMAP Mailboxes to Microsoft 365 Manually

Main Steps Included to Migrate IMAP Mailboxes to Microsoft 365 Manually

  1. Finding the Current Email Server Name
  2. Creating a Mailbox List for Migration
  3. Connecting Microsoft 365 to Email System
  4. Performing the Migration
  5. Routing Emails to Microsoft 365 Account Directly
  6. Deleting the Migration Batch

Important tasks before migration: Users are required to add the domain to Microsoft 365 account as an accepted domain if the IMAP email system is using an email domain. Then new users (with the same source mailboxes name) need to be created in the Microsoft 365 which act as a target mailbox for the source  IMAP migration

1st Stage – Finding Current Email Server Name

For the mailbox migration, Microsoft 365 requires the name of the current source email server which can be determined or fetched utilizing the Outlook on the web application.

Just launch the Outlook on the web application on your browser. Click the Settings option from the toolbar. Search for POP and IMAP Settings in the search bar and open the POP and IMAP Settings page. From the IMAP setting section, note down the IMAP Server name which is the source email server name that you require.

2nd Stage  – Creating a Mailbox List for Migration

Next, create a list of mailboxes in the source IMAP Server which users want to migrate to Microsoft 365 user mailboxes with the same name. This list can be created in an Excel file and saved in the .csv file format.

To know which mailboxes to migrate, keep the source email server open with the list of mailboxes opened. Simultaneously, log into the Microsoft 365 account and follow Admin center>Users>Active users.

Now open the Excel file and enter details of the mailboxes for migration– EmailAddress, UserName, Password.

Note: Users can enter up to 50, 000 rows (user mailboxes) for migration.

Save this Excel file in CSV format at any convenient location.

3rd Stage – Connecting Microsoft 365 to Email System

To carry out the migration between Microsoft 365 and IMAP Server email system, users need to establish a connection with the help of migration endpoint which contains the details about the connection settings within it. Follow this process to create a connection.

  1. Go to the Microsoft 365 Admin Center and under Admin Centers section, select the Exchange option. This will open the Exchange Admin Center.
  2. Select recipients and then move to the migration tab. Click on 3 dots (More option) and select Migration endpoints.
  • Create a new migration endpoint by clicking on the New option. Choose IMAP as the migration endpoint type. Provide IMAP messaging server name of the source IMAP server and click Next.
  • Next, on the Enter general information page for the new migration endpoint, enter any name for the migration endpoint, leave the rest options blank and click new.
  • A new migration endpoint will get created.

4th Stage – Performing the Migration

This is the stage where emails from the list of mailboxes would be migrated to Microsoft 365 destination mailboxes. First, users have to create a migration batch and then start migrating this batch. Here are the sequential steps of the process.

  1. Reach the Exchange admin center again in your Microsoft 365 account.
  2. Navigate recipients>migration. Click the New option and select Migrate to Exchange Online from the drop-down list.
  • Select IMAP migration as an option and click Next.
  • Click Browse option against Select the users page section and add the CSV file containing the details of mailboxes. After adding the file, click Next.
  • Click Next to continue.
  • On the next page, add the migration endpoint created in the previous stage.
  • The Move configuration page will get opened, provide a name for the migration batch and click Next. Choose and add folders that you want to exclude (optional) and click Next.
  • Select Automatically start the batch option from the Start the batch page to start the migration at once.
  1. Check if the task is successfully completed by visiting the recipients>migration and moving to the migration batch. If its status is Synced, then the migration was successful.

5th Stage – Routing Emails to Microsoft 365 Account Directly

While migrating emails from the source server to Microsoft 365, the MX record (for determining messages delivery direction) was pointing to the source email server which has to be changed to the Microsoft 365 after the migration is completed.

Note: Users performing the migration are required to wait for 72 hours before proceeding to the next stage as the email systems would take about this much time to recognize the modified MX record.

6th Stage – Deleting the Migration Batch

After about 72 hours of changing the MX record, users can delete the migration batch which ensures the deletion of the migration batch records from the migration dashboard. Follow these steps to delete the migration batch.

Go to the Exchange Admin Center from the Microsoft 365 admin center, follow recipients>migration. Select the migration batch from the migration dashboard, click on the Delete icon to delete it finally.

Hence, these were all the stages in the manual migration of IMAP mailboxes to Microsoft 365. This method works well for the users if followed patiently and carefully. All the steps in the stages are important and need to be performed correctly to avoid any issues during the migration. There is another manual option where users can perform IMAP migration to Microsoft 365 with PowerShell commands.

We have an alternative way to move IMAP server mailboxes to Microsoft 365 without waiting or worrying about multiple steps and multiple stages. We suggest Kernel IMAP to Office 365, the most effective and direct IMAP to Microsoft 365 migration tool, to all users. It supports Office 365 migration of almost all IMAP servers.


The manual migration of IMAP mailboxes to Microsoft 365 using its interface is a multi-staged process. Users do not get instant migration and have to wait long to complete the process. So, to avoid this, choosing a professional tool (as explained in the blog) is the best option.

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