Migrating Emails from IONOS Mail Accounts to Microsoft 365

For customers with IONOS Mail Basic and IONOS Mail Business mailboxes.

In this article you can learn more about migrating e-mails from IONOS Mail Basic and IONOS Mail Business mailboxes (IMAP) to Microsoft 365.

Restrictions regarding the import

  • The maximum size of an e-mail must not exceed 35 megabytes.
  • A maximum of 500.000 elements can be transferred per user mailbox.
  • Only e-mails will be migrated, no contacts, tasks, etc.

Getting ready for the migration

To transfer the user data of the IONOS mailboxes to Microsoft 365:

  • Open any program that allows you to create comma-seperated CSV files, e.g. Microsoft Excel.
  • Enter the following headings per column in the first line: EMailAddress, Username, Password 
  • Add a line with the user data for each user mailbox.
  • Save the file in CSV format (seperator: comma).

Performing the migration

  • The users to be imported must already be created in Microsoft 365.
  • As of the beginning of 202, Microsoft has changed the design of the Exchange Admin Center. The following step-by-step instructions refer to the menu structures and options of the classic display.
  • Log in to your Microsoft 365 administrator account.
  • Select the Admin icon in the left menu. The Microsoft 365 Admin Center opens.
  • Select Exchange in the left menu. Note that you may have to display the menu with Show All completely.
  • Click on the Classic Exchange Admin Center button to find the correct menu structures and options for the following steps.
  • Under Recipients, click Migration.
  • Click the ... button and select Migration Endpoints. The Migration Endpoints window opens.
  • Click on the plus  symbol to create a new migration endpoint. The Migration Endpoint Assistant window now opens.
  • Select the Migration Endpoint IMAP and click Next.
  • In the IMAP server field, enter imap.ionos.com and confirm the entry with Next.
  • In the field Migration endpoint name, enter the desired name of the migration endpoint and click New.
  • Close the Migration Endpoints window.
  • Click on the plus symbol and select Migrate to Exchange-Online. The New Migration Batch window opens
  • Select the IMAP migration item and load your prepared CSV file.
  • Complete your entry with Next.
  • Enter a name of your choice in the Name of new migration batch field and click Next.
  • To start the migration, click New. You can now close the Exchange Admin Center. The migration process continues in the background.

You have migrated your e-mails from IONOS Mail Basic respectively. IONOS Mail Business to Microsoft 365.