ID #81026

Migrate historical email to Office 365 using IMAP

This guide shows you how to migrate historical email to Office 365 using IMAP.


1. Login to MyAccount Control Panel, go to O365 and choose Users.

 MyA 0365 Users


2. Choose Create new 0365 account in Office 365 Administration. MyA 0365 Create New Account


3. Your Office 365 mail has been created. Now start moving all your historical emails. 

Create an .csv file in the following format or right click the Download Link and choose Save as Target to download our example file.


Download Link



EmailAddress: your new Office 365 Accounts

UserName: your current email adress and the account emails are synchronized from

Password: your current password for the old Businessmail, IMAP or POP account.

Important: You should NOT specify you new Office 365 password in this file.


4. Log in to Microsoft Online Portal as administrator. 

a. Choose Admin and Exchange

How to migrate historical email to Office 365 using IMAP


b. Choose Migration

Office 365, Exchange, IMAP, Migration


c. Click plus sign (+) and choose Migrate to Exchange Online

 Microsoft Online Portal - Migrate to Exchange Online


d. Choose IMAP migration and click next.

IMAP migration to Office 365


e.  Browse for the .csv file (created in step 2)and upload. Click next.

The page should look like image below:

Office 365 Migration - Upload .csv file

In this example we are migrating 4 email accounts.


f. Enter following IMAP settings then click next:

Office 365 migration - IMAP settings


g. Choose a Migration bach name (example: Office365 migration) and Click next.


h. Choose Start Migration Now or Start Migration Later. Click next to complete the wizzard.


Things to consider


  1. Do not delete emails in the old email account that you want to keep, because they will also be removed in Office 365.To ensure no emails are lost, the old email account and new Office 365 account will be synced again after 24 hours.
  2. Calendar and Contacts will not be migrated. Since this is an IMAP migration, Contacts and Calendar was not synced in the old solution and will therefore not be transfered over to Office 365 either.
  3. E-mail messages larger than 35 MB won't be migrated. You should save very large messages and attachments to your local computer or to a removable USB drive.
  4. Delete old or unnecessary e-mail messages from your current mailbox before migration, when your mailbox is  very large. This helps to reducing the amount of datamigration and reduce overall migration time.
  5. Back-up your Inbox before starting migration.
  6. Folders with a forward slash ( / ) in the folder name aren't migrated.If you want to migrate folders that contain forward slashes in their names, please rename the folders or replace the forward slashes with a different character, such as an underscore character ( _ ) or a dash ( - ).