How to Migrate IMAP Emails to Office 365?

Himanshu Goyal
Himanshu Goyal linkedin | Updated On - February 17, 2022 |

Read time 12 minutes

Office 365 is a cloud-based service from Microsoft that compasses various services and applications that alleviate the productivity of any business and big enterprise. The subscription plans of Office 365 are divided based on the applicability of the application and the size of the company. The security of the account is based on the shared model where Microsoft takes care of the availability and accessibility of resources. Users can maintain who can access the account and their level of permissions.

Regular email accounts do not provide such detailed security features. When users want to move their emails to Office 365, you should know the detailed platform information of both source and destination.

In our previous blog, we talked about how to perform IMAP migration to Office 365 with PowerShell commands. here we will talk about migrating other IMAP emails to Office 365, but there are some things that you need to know before migrating your IMAP emails to Office 365.

Things to Know before IMAP Migration

A few limitations are applied to IMAP to Office 365 migration, which includes:

  • Only user’s inbox and other mail folders can be migrated to Office 365. This method cannot be used to migrate calendar, contacts, or tasks
  • A maximum of 5,00,000 data items from a user’s mailbox can be migrated
  • Maximum email size limit for migration is 35 MB
  • You’ll have to create users in Office 365 first, and then migrate IMAP mailboxes
  • To use a similar email domain of IMAP in Office 365, you’ll have to add the domain to Office 365 before creating users. You can check how to add users individually or in bulk to Office 365.

These are a few limitations that you must be aware of before migrating your IMAP emails to Office 365. Now, let’s move to the steps involved in migrating IMAP mailboxes to Office 365.

Steps for Migrating IMAP to Office 365

There are six steps involved in migrating other IMAP email accounts to Office 365, and performing each of these steps is crucial for flawless migration of mailboxes. The steps include:

Following these steps, you’ll be able to migrate your IMAP data to Office 365 account.

Step 1: Identifying the Full Name of Your Current Email Server

Office 365 requires the same source email server name for migration, so you’ll have to identify the full name of your current IMAP email server.

  1. Open your mailbox with Outlook on the web.
  2. Go to Settings in the toolbar, and then type “pop” in the Search all settings box.
  3. From the result displayed, select POP and IMAP.
  4. The IMAP server name will be listed in the IMAP setting section.
    IMAP server name
Step 2: Creating a List of Mailboxes to Migrate

Before migrating the mailboxes to Office 365, you need access to your IMAP user mailboxes. For this, create a list of mailboxes when you know the password of user mailboxes. This information can be collected from your source email system. If you don’t know the user passwords, you can reset the passwords to new passwords.
Reset the password

Step 3: Connecting Office 365 to Your Email System

To connect with the source email system, Office 365 uses a migration endpoint. You can create the migration endpoint with the following steps:

  1. Go to Exchange Admin Center and click Recipients.
  2. Select Migration >> More …>> Migration endpoints.
    Select migration endpoint
  3. To create a new migration endpoint, click the New + icon.
  4. The Select the migration endpoint type page will appear on the screen, click IMAP.
  5. Enter the following details to IMAP migration configuration page:
    • IMAP Server name
    • Leave rest information as it is and click Next
  6. The migration services will test the connection to the email server, and if it works, the Enter general information page will appear on the screen.
  7. On this page, type the Migration endpoint name. Leave the other boxes completely blank and click New to create the migration endpoint.

The new migration endpoint will be created after that.

Step 4: Creating a Migration Batch and Migrating Mailboxes

You need to create a migration batch for bulk migration of emails to Office 365 mailboxes. This migration batch will consist of the mailboxes that you listed in the migration file earlier. Follow the below steps to create a migration batch.

  1. Go to Exchange Admin Center and click Recipients >> Migration.
  2. Click New + >> Migrate to Exchange Online.
    Migrate to Exchange online
  3. Select IMAP migration and click Next.
  4. The Select the user page will appear on the screen, click Browse to select the migration file that you created. Office 365 will run a quick check on the file to verify whether it’s accurate or not.
  5. If the file is verified by Office 365, the number of users listed in the file will be displayed as the number of mailboxes to migrate. After file validation, click Next.
    Select the mailbox to migrate
  6. The IMAP migration configuration page will appear on the screen, click Next.
  7. Now, select the migration endpoint that you created in step 3.
  8. Go to Move Migration page, type the name of the migration batch, and then click Next. From here, you can also exclude the folder from the migration process by typing their name or clicking the “+” icon. After making your selection click Next.
    Type the name of migration batch
  9. The Start the batch page will appear on the screen, take the following actions:
    • Click Browse for sending a copy of migration reports to other users. The migration report can also be accessed from the properties page of the migration batch.
    • Select Automatically start the batch. The migration process will begin when you save the migration batch. The status of the migration batch will change to Syncing from Created.

You can verify the status of the task in the Exchange Admin Center.

Step 5: Directly Route Your Email to Office 365

Every email system uses a DNS record (called MX record), to identify the delivery address for emails. During the email migration process, the MX record is left pointing toward the source email system. After the successful migration to Office 365, you’ll have to point MX record at Office 365. It will ensure that all the emails are delivered to your Office 365 mailboxes.
Generally, it takes around 72 hours for the email systems to recognize the changed MX record. Once it is complete, you can move to the next task to stop email synchronization, but make sure you wait at least 72 hours before moving to the next step.

Step 6: Discontinuing Email Synchronization

After changing the MX records, you’ll have to verify that all your emails are being routed to Office 365, and then only you’ll be able to delete the migration batch. Doing so will discontinue the synchronization between your source email system and Office 365. But before that, here are a few things that you need to check:

  • Your users are using Office 365 for email. After deleting the migration batch, the emails sent to your source email system aren’t copied to Office 365.
  • Before deleting the migration batch, let it run for at least 72 hours. It will give enough time for synchronization between your source email system and Office 365 mailboxes.

After deleting the migration batch, the migration service will clear the records related to the migration batch and eliminates it from the migration dashboard.
Deleting a Migration Batch
You can easily remove a migration batch from the Exchange Admin Center.

  1. Visit the Exchange Admin Center and go to Recipients and then select Migration.
  2. From the migration dashboard, click Delete for the selective batch.

Delete the selective batch
You can confirm the deletion of migration batch by again visiting the Recipients in Exchange Admin Center.

Seeing the above steps, do you think it’s easy to migrate your IMAP mailboxes to Office 365 with this approach? Surely not. Also, we cannot say that the migration of mailboxes will be successful with this approach because if there is any problem with the migration batch, then you’ll have to repeat the process. So, what’s best for you is to choose an IMAP to Office 365 migration tool that can quickly migrate your mailboxes without much hassle, and one such tool is Kernel IMAP to Office 365 that is specifically designed for the same. Using this software, you can quickly migrate your IMAP mailboxes to Office 365 within a few minutes. Let’s have a quick look at the working process of this IMAP migration tool.

Kernel IMAP to Office 365

Using this IMAP migration tool is pretty simple, it involves a few steps, and you will successfully migrate your IMAP mailboxes to Office 365 quickly. Also, you can migrate from 20+ IMAP accounts, including Gmail, Yahoo, AOL, Zimbra, etc. Here, we will discuss the process of migrating Gmail mailboxes to Office 365.

First of all, you need to download and configure the software on your system. After installing it, follow the below steps:

  1. Launch the tool and click Add in the Add Source section.
    Launch IMAP to Office 365 migration tool
  2. Provide the details for your Gmail account and click Add.
    Provide details of Gmail account
  3. After adding the Gmail account, click Add in the Add Destination section to add Office 365 account.
    Add Office 365 account at destination
  4. Enter the credentials for Office 365 account, select the Single Mailbox/Office 365 group option, and click Add.
    Enter Office 365 credentials
  5. After adding the mailboxes, map both source and destination mailboxes to each other and click Set Filter and Migrate.
    Map source and destination mailbox
  6. In the next step, select the type of mailbox to which you want to Migrate Gmail data and click Migrate.
    Select the type of mailbox which you want to Migrate
  7. The Filter Selection window will appear on the screen, apply filters to the mailbox data as per your requirements, and then click I am OK Start Migration.
    Apply filter option
  8. The software will start migrating Gmail mailboxes to Office 365. After it is done, a notification will appear on the screen confirming the same. Click OK to end the process.
    Start the migration from Gmail mailbox to Office 365

That’s how you can easily migrate the Gmail mailbox to Office 365 account quickly with the help of Kernel IMAP to Office 365 migration tool. This utility also allows you to skip already migrated data.


Many organization ions are moving from IMAP to Office 365 for enhanced productivity and security. In such scenarios, migrating with a right approach is necessary. That’s why we have mentioned a technique of IMAP migration in this blog. However, we also recommended a third-party IMAP migration tool that makes IMAP to Office 365 migration quicker.

Video Tutorial About How to Migrate IMAP Emails to Office 365?