Strangest issue i've seen on exchange.
We have exchange server 2013 with CU 21. All of our users have an separate contact with an external email address. An email is sent to a distribution list that only has internal email address members. The distribution list is not expanded in the to line of outlook so it still says "marketing users". At the some point during the messages recipient resolution process, it uses the external contact address for some of the members of the distribution list. (6 of 53)
i've verified the distro has the correct member emails. i've verified via get-messagetrackinglog that the server is expanding the distro list and using the contact address on the 6 emails. at this point, i'm going to reboot the servers tonight (they need a reboot) and resend to the distro list and see if it happens again? any thoughts?