Some Assistance Please!

I’m assuming that all the rt.mydomain.com and myserver.mydomain instances are in fact place holders for posting purposes. They should in fact be rt.lakeheadu.ca (pulled from the error messages you posted).
You may also want to add “–debug” to the end of the alias - at least temporarily.
“Temporary failure” from rt-mailgate means it either can’t talk to the web server (not found) or that the ticket could not be created (permissions). The mail system should requeue the mail and try again later.

The hostname is rt.lakeheadu.ca. I was trying earlier to keep that out of the posts as per best practice, but at this point I don’t care. I will try the debug at the end of that statement

One question came up in trying to troubleshoot this that may have gotten lost in translation.

If a user who already has an account registered on RT, and they submit an email to a queue to create a ticket, does that action entirely bypass authentication back to the server?

Say user 123 submits a ticket to ServerAdmin with a subject line and content and user has an account on RT (unprivileged), does RT_mailgate run in the background behind the scene to make sure that info is captured in a ticket? What if user 123 doesn’t have an account on RT and performs the same action

If an account doesn’t exist RT will make a unprivileged user record when the email comes in

Even if we have SSO running via shibboleth?

Yup everything in RT must be done by a user, these autocreated users cannot login though since they are just unprivileged users with no passwords. If “everyone” has the right to create or reply to a ticket then they can email in and create/reply to a ticket.

shibboleth auth is only used for login and maybe REST API stuff.