Notice re: transition to MacMail
During the transition from UnivMail to MacMail, a sender may receive an “undeliverable” return message. This issue may be related to the email address in your Outlook cache, which may contain references to UnivMail.
You may need to clear your Outlook suggested cache. For support, refer to: https://support.microsoft.com/en-us/kb/287623/
Note: after clearing your cache, you can use the standard email address format (macid@mcmaster.ca) or if both sender and recipient are on MacMail, the sender could choose the email address from the GAL.