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Your Exchange Online account is now added and visible on the Accounts page. Ensure username and password fields are not blank, and that the email address you wish to send from (typically your @medschl address) is correct. Now close the box:
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Your email, calendar and tasks will begin to download to your computer. Please note that depending on the size of your mailbox this can take quite a while. Please be patient.
Once you are happy that your newly added account is working correctly, you can go ahead and remove your old account by coming back to the Accounts box, highlighting the old account, and clicking the minus button (doing so removes it from Outlook on your Mac only).
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