I have created a distribution group with the an address of email@example.com. I added external contacts to the DG. The external contacts have domains of @abc123.com as well as @yahoo.com and @gmail.com. When I send to each contact individually, without the use of the distribution group, all emails arive to the contact addresses. When send to the distribution group only the @gmail.com and @yahoo.com addresses receive the mail. The emails are never received by @abc123.com addresses.
abc123.com has never been verified. Any suggestions?