1) Sign into an admin level account for the domain's SmarterMail.

2) Click the Accounts Tab.

3) Locate the user with a red triangle next to their name. In order to re-attach the user you must first remove them, after the user has been removed you can proceed to step 4.

4) Click the three dot Actions button then click Attach User.

5) Enter the email address of the user you need to re-attach then click Attach.