I've searched serverfault and found this question pop-up quite a bit. Unfortunately others problems aren't exactly like mine, and because I'm a true beginner I wanted some more "specific to me" help. If you don't mind.
I just set-up a new computer for a user. Copied over her auto-populate and archive emails. Her email, for the most part, works fine. But when she tries to send anything to BSMITH@mydomain.com she gets the #550 5.1.1 error. If she uses the exchange webapp she does not have the issue. I can send email to BSMITH, and so can everyone else. The user, as far as I can tell from the EMC reports, is the only person having emails sent back to them and only from BSMITH.
I have googled the crap out of this, and attempted some of the solutions to no avail. I've looked for the bmith account in the disabled accounts and copied and attempted to add "IMCEAEX-_O=CHILD+20STUDY+20CENTER_OU=FIRST+20ADMINISTRATIVE+20GROUP_CN=RECIPIENTS_CN=BSMITH@mydomain.com" as an X500 email.
I honestly am just following instructions though and I don't really understand what it is I'm doing.
Diagnostic information for administrators:
Generating server: FS2.FS1D.local IMCEAEX-_O=CHILD+20STUDY+20CENTER_OU=FIRST+20ADMINISTRATIVE+20GROUP_CN=RECIPIENTS_CN=BSMITH@mydomain.com #550 5.1.1 RESOLVER.ADR.ExRecipNotFound; not found ##
BTW I love this site and only found out about it a few weeks ago. My girlfriend now loves the photo.stackexchange. So thanks for such a helpful community.