How to migrate from an IMAP server to Office 365?

On the Internet, you can find tons of guides, which explain how to migrate from an IMAP server to Office 365. Most of them cover the topic from the native perspective, so to contrast this, I am going to show you how to perform IMAP migration to Office 365 by using a third party tool – CodeTwo Office 365 Migration.

IMAP migration to Office 365
To migrate emails from an IMAP server like e.g. IBM Lotus, G Suite or Zimbra to Exchange Online, you need to do some preparation first. In this phase, you are about to prepare source and target servers and users for migration. Once, you are ready with that, you can start the actual migration using CodeTwo migration tool. This phase is as simple as setting up the program and clicking the Start button. As soon as users’ emails are migrated to Office 365, you can start post-migration cleanup. Keep reading to learn more on why CodeTwo Office 365 Migration makes IMAP migration easier and quicker than a native solution and how to perform this migration process step by step.

CodeTwo Office 365 Migration vs native IMAP migration

To migrate emails from an IMAP server, you can use either native Office 365 migration feature or a third party tool like CodeTwo Office 365 Migration. All depends on your resources (e.g. time), budget and preferences. Native migration requires more attention and preparation. It also takes longer, mainly due to fewer possibilities to automate the process.

Below I point to a bunch of benefits that you get with CodeTwo migration tool in contrast to when following the native migration path. CodeTwo Office 365 Migration allows you to:

  • Automatically create users and mailboxes on the target Office 365 server, which is a great time-saver (no need to do it manually).
  • Automatically match IMAP and Office 365 mailboxes.
  • Overall, mailbox or job reports as well as instant alerts in the program inform you about the migration performance. You can also get reports directly to your Inbox.
  • Delta scan feature (Rescan) that allows you to re-run migration for already moved mailboxes to transfer newly arrived emails. This will not create any duplicates on the target server.
  • Create separate migration batches called migration jobs to better organize the whole process. You can easily manage all jobs via the 100% graphical user interface.
  • Schedule migration so that it runs automatically. You can set up this functionality individually for each migration job.
  • Pause and resume migration at any moment.

How to migrate to Office 365 from an IMAP source?

Below you will find a step-by-step instruction on how to perform the IMAP migration of emails to Office 365 with CodeTwo Office 365 Migration software.

Pre-migration tasks when migrating from the IMAP server

Before you start the migration:

  1. Create the custom domain in Office 365 and verify it. Here is the instruction that shows how to do it.
  2. If you are migrating to Office 365, you need to recreate IMAP server users in Office 365. You can either do it manually or let CodeTwo Office 365 Migration do it for you automatically.
  3. Make sure your admin account that you use to connect to the target tenant has all necessary roles assigned. More info about required roles, you can find in this user’s manual article.
  4. Check whether your Office 365 admin’s email address is set to active with a new domain. To check this, navigate to Admin tab/Office 365 section/Users and Groups > select Admin’s account and check Details.
  5. Now it is time to assign Office 365 licenses to user mailboxes. However, when using CodeTwo Office 365 Migration, the program can automatically create mailboxes and assign the Office 365 licenses to them. If you prefer to do this manually, here is the instruction.
  6. Due to the IMAP protocol limitations, you need to prepare a CSV file containing users’ mailbox credentials.
  7. Get ready to know your IMAP email address or IP, port and whether SSL connection is supported. Here is an example for Gmail: gmail.comport 993enabled SSL. If you are migrating from G Suite, see this instruction on how to enable IMAP access on the source server.
  8. Download, install and activate CodeTwo Office 365 Migration.

Migration process

The migration process itself is as easy as configuring the CodeTwo migration tool. Follow the steps below to set up the program:

  1. Once you open the program, in the Dashboard view, on the How to start card, you will see a Create a new migration job link. Click it and select Migration job from IMAP server… to start the migration job wizard.Create a new migration job
  2. Set the migration job name and click Next.
  3. Configure the connection to your source IMAP server. In this step, you need to provide the server details you collected in step 7 above. Click Next to close this window and go back to the migration job wizard.
    IMAP server connection
  4. In the Source mailboxes section, you need to define which mailboxes you want to migrate from IMAP to Office 365.

    Note: Here you need to use your CSV file with source mailbox credentials. The file should consist of the following fields: EmailAddress, UserName, Password. To import the file use the Import CSV option and configure the software so that it properly reads your data. For testing purposes, it is a good practice to first migrate 1-2 test mailboxes (e.g. your mailbox) to see if everything is set up correctly and there are no roadblocks on the way.
  5. Now, connect to the target Office 365 tenant. You can connect to either Office 365 worldwide or Office 365 Germany.
    Target Office 365 connection
  6. Once you configured server connections, you can now match source and target mailboxes. You can either match them manually or automatically using the Automatch option.
    Automatch options
  7. Configure other options of the migration job, which are Scheduler, Time filters, Folder filters and Advanced settings.
  8. Once the migration job is ready, simply click Start in the top menu to begin the migration process.

    Note: As for migration speed, it may differ depending on the individual environment settings. To see what factors can impact migration speed and performance, follow this link.
  9. After migration is finished, check if items on the source and target servers show the same results. If you notice any missing items on the target server, you can run the Rescan feature to migrate all remaining emails to Office 365.

    Note: During the migration, the Rescan feature is greyed out. Once selected migration job is finished, you can rescan it for missing items.Rescan option
  10. Use the Rescan option also if you notice some new items delivered to source mailboxes during the migration process. This will let you move newly arrived emails even if migration of a particular mailbox has already finished.

Post-migration tasks

Once you migrated all emails to Office 365 from your current IMAP server, it is time to change MX records to point mail flow to your new Office 365 server. This process may take several hours. If during the MX records switch you will notice new items in the source mailboxes, use the Rescan option to move them over.

Note: If you are migrating to a completely new domain, there is no need to change MX records. In other words, once the migration is finished, there are no post-migration activities.

For a more detailed instruction on migration from an IMAP source to Office 365, see this user’s manual.

If you would like to give the program a try, download and run a free trial version of CodeTwo Office 365 Migration. No commitments.

On this website, you can find more information about the program.

IMAP migration – limitations

When migrating from Rackspace, G Suite, IBM Notes, Zimbra or any other IMAP server, it is good to be aware of the limitations that you will hit:

  • IMAP migrations can only move emails. Other mailbox items and folders (like calendars or contacts) are not supported in this migration type.
  • You need to prepare a CSV file with source mailbox credentials prior to migration. This ensures access to user mailboxes.
  • You can migrate emails the size of which is less than 35 MB.

These limitations originate from the way IMAP protocol handles the migration.

See also:

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