During the migration process, Apple mail will continue to function normally. At the end of the move, the mailbox will enter the completing phase which will lock the mailbox on the server. This will cause Apple mail to fail to connect to the server. When sending or receiving a message, the following notification may be displayed:

Once this message pops up, click Try Later, and go to Mail > Preferences. This will display the accounts. Select the Exchange account and use the “–“button on the bottom to delete it. Once it is deleted, use the “+” sign to create a new account.

On the following page, enter your email address and password in the blanks provided. Apple mail will automatically determine the correct server settings.

Give the account a description, select the services desired, and click continue.

Note: Apple mail may need to be closed and re-opened in order for all settings to fully take effect. This may be necessary if the email gets stuck in the Outbox or new email is not being received.