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Office 365 is a cloud-based service developed by Microsoft to help businesses increase their productivity with a range of applications and features. The subscription plans are customizable and cater to all types of businesses. The security model is devised for account protection, which enables users to control who can access the account and what type of access they have.

On the other hand, standard email accounts lack many necessary security features. When shifting from standard email accounts to Office 365, it is essential to understand both the source and destination of the platform thoroughly.

Previously, we explained how to perform IMAP migration to Office 365 with PowerShell commands. Now we will talk about essential things to keep in mind while migrating other 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 inboxes 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.

Before embarking on the process of migrating your IMAP emails to Office 365, it’s crucial to acquaint yourself with some notable limitations. With that awareness in mind, let’s delve into the sequential steps required for a successful migration of IMAP mailboxes to Office 365.

Steps for migrating IMAP to Office 365

Migrating other IMAP email accounts to Office 365 entails a structured process comprising six essential steps. The successful execution of each of these steps is imperative for achieving a seamless migration of mailboxes. These key steps encompass:

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

Prior to migrating your mailboxes to Office 365, it’s essential to ensure you have access to your IMAP user mailboxes. To achieve this, begin by compiling a comprehensive list of mailboxes for which you possess the user mailbox passwords. This crucial data can be obtained from your source email system. In cases where the user passwords are unknown, you have the option to reset them to new, secure 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 the 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

To facilitate the bulk migration of emails into Office 365 mailboxes, it’s essential to set up a migration batch comprising the mailboxes previously designated in the migration file. Follow the steps outlined below to initiate the creation of this migration batch.

  1. Go to the 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 the 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 relies on a DNS record known as an MX record to specify the destination for email deliveries. In the course of email migration, the MX record initially directs email traffic to the originating email system. Following the successful migration to Office 365, the MX record must be redirected to Office 365. This step guarantees the smooth delivery of all emails to your Office 365 mailboxes.
Typically, it takes approximately 72 hours for email systems to acknowledge the MX record modification. Once this process is complete, you can proceed to the subsequent task of halting email synchronization. However, it is essential to exercise patience and wait for at least 72 hours before advancing to the next step.

Step 6: Discontinuing email synchronization

Once the MX records have been updated, it is essential to ensure that all your emails are correctly directed to Office 365 before proceeding with the removal of the migration batch. This step is crucial as it will terminate the synchronization between your source email system and Office 365. To facilitate a smooth transition, there are several key factors you should examine beforehand:

  • 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 the migration batch by again visiting the Recipients in the Exchange Admin Center.

After reviewing the steps outlined above, does it seem straightforward to migrate your IMAP mailboxes to Office 365 using this method? You know, it’s not as easy as it may appear. Moreover, the success of the mailbox migration isn’t guaranteed with this approach; if any issues arise during the migration batch, you might find yourself repeating the entire process. To ensure a smoother and more reliable transition, we recommend opting for a specialized IMAP to Office 365 migration tool like Kernel IMAP to Office 365. This software is purpose-built for this task and can efficiently migrate your IMAP mailboxes to Office 365 with minimal hassle. With this utility, you can complete the migration within a matter of minutes. Let’s take a brief look at how this IMAP migration tool operates.

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 the 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.


Migrating IMAP emails to Office 365 is a crucial task for users who want to enjoy the benefits of a better email management system. As we have discussed the steps to perform this migration, Kernel IMAP to Office 365 software is the most reliable and efficient solution.

With its advanced features, this software guarantees data migration with full security. So, if you are in need to move your IMAP emails to Office 365, it is definitely the way to go. Give it a try today and experience the difference.


Q- How often does IMAP migration sync with Office 365?

A- After a successful migration, the synchronization between the IMAP server mailbox and the Exchange Online mailbox happens once daily (every 24 hours). This process is referred to as incremental synchronization and continues until the migration batch is stopped or deleted.

Q- Why should you disable IMAP and POP3 Office 365?

A- These legacy email protocols are frequently targeted by hackers attempting to gain unauthorized access to mailboxes. By disabling them, you can keep your sensitive information safe and secure along with protection against data breaches and other malicious activities.