I am trying to configure a secondary address for staff members. Accepted Domains at the start of this were: someschooldistrict.org (Authoritive) *.somesd.org (external relay) This is the domain that I want to configure as a secondary address for staff. my.somesd.org (external relay). This last domain is student email hosted by a third party. Students are contacts in our Exchange so that they show up in our GAL. These are the configuration changes I made: DNS records configured for the somesd.org domain pointing the MX to our Exchange server: mail. someschooldistrict.org Removed the *.somesd.org from Accepted Domains and created somesd.org as a new Accepted Domain (Authoritive). Created a new E-mail Address Policy using the alias and the somesd.org domain, which correctly added the new email address to staff accounts. Here’s where I run into a problem. Attempting to send to that same address from hotmail or yahoo accounts fails. Yahoo is more descriptive: Remote host said: 550 Relay not permitted [RCPT_TO]. What have I missed?

Fixed it. A firewall upstream at our provider needed the additional domain added to the list.