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Microsoft 365 - Email and Calendaring - Migration Checklist

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Migration Overview

The official schedule for the Microsoft 365 migration has not been finalized, however, our initial plan includes moving departments and working groups at the same time. Our plan includes staging an individual's mail on Microsoft 365 the evening before the actual migration and then completing the move the next morning. Communication will occur the week before the migration, with reminders the day before, the day of, and a final acknowledgment after the individual has migrated to Microsoft 365.


These are the actions to take at every step of the migration process to ensure a smooth transition to O365 and a minimum of disruption in your daily work.

Before You Migrate

  • Outlook Client Support for Microsoft 365 - If you are running an older version of Outlook you will need to update your desktop client. Microsoft 365 only supports the most recent versions of Outlook which are:
    • Outlook 2010/Outlook 2013/Office 2016 (Windows)
    • Outlook 2011/2016 (Mac)
  • Username Change for Microsoft 365 - Microsoft 365 requires that the username used from Outlook and Mobile device clients use the following username format
  • Delegates and Delegating - Check with anyone you delegate with to make sure you are all scheduled for migrations at the same time. Delegation does not work between the two email systems.
  • Clean up your mailbox - Your transition will be easier and quicker if your mailbox is clear of clutter. Go through your Inbox and all folders, including the Sent folder, to delete any messages that are no longer necessary. Then empty your Deleted Items folder.
  • Take inventory of any existing mailbox and/or calendar permissions - Now is a good time to check that permissions and access are up to date on any accounts, mailboxes, folders or calendars that you have shared or that have been shared with you.
  • Identify and your shared calendars and delegates. Anyone you share or delegate calendars with needs to move to Microsoft 365 when your group moves to Microsoft 365.
  • Print this checklist - We recommend that you print this document to have the Day of Migration required steps on hand for reference during your migration.

During Migration

  • Continue to use your email and calendar normally as you will have full access to your exchange mailbox on the evening before the move, however, you may experience a brief interruption on the morning of the move when the final cutover is moved into place.

After You're Migrated

  • When the migration is complete, you may receive an error message if you did not update your username prior to migration, or if you are using the web client or Apple Mail/iCal. If so update your username on any clients or devices now to be your full email address, Apple Mail/iCal and Web Client users see below.
  • Apple Mail/iCal Users - If you use Apple Mail and/or iCal, you will need to delete and recreate your account. See: Microsoft 365 - Email and Calendaring - Apple Mail and iCal Configuration
  • If your new web email/calendaring client is Outlook on the Web. - For information on logging in and using it, see: Microsoft 365 Email and Calendaring - Outlook on the Web Landing Page
  • Calendar Notifications for past events may pop up shortly after you are migrated. This is a one-time thing. Dismiss them. This issue should not recur.
  • Confirm that you can access any shared and/or delegate mailboxes that were migrated with your group If there are shared mailboxes or delegate permissions that you know were scheduled to be migrated with your group, confirm that you can access those accounts. If you cannot, contact [istdraft:TBD]

Known Limitations Relating to Microsoft 365

  • Email: If you have delegated permissions to a mailbox that has not been migrated to Microsoft 365, you will not be able to Send As from that mailbox. Once the migration of your account and the shared mailbox are complete, you will regain the ability to perform delegated tasks for the other mailbox.
  • Calendar: Microsoft 365 users will be able to see Free-Busy information but will not be able to manage calendars for users that have not migrated to Microsoft 365, and vice versa.

See Also

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Last Modified:

August 02, 2023

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