1. Log into said user on Zimbra.
2. Navigate to "Preferences".
   1. 
3. Navigate to "Accounts".
   1. 
4. Navigate to "Add External account".
   1. 
5. Fill in MS365 Email address under "Email address"
6. Under account name, use "MS365"
7. Select "IMAP" as account type.
8. Fill in username and password of MS365 Account.
   1. Note: This is not the login information for Zimbra, but the login information for the preexisting MS365 account.
9. Fill in "outlook.office365.com" as email server.
10. Select or deselect encrypted connection based on needs.
11. Your settings should look like this:
    1. 
12. Select "Test Settings" to make sure it works
    1. If you get an error quickly(0-2 seconds), you most likely misspelled the username.
    2. If it takes very long, you most likely misspelled the email server name
13. Save.
    1.