I have a long-time email address admin@xxxx.com I can’t abandon, so set up a mailbox admin.xxxx@xxxx.com with an alias of admin@xxxx.com.
So far, so good. However a from address admin.xxxx@xxxx.com works but a from address of admin@xxxx.com does not. Is this because admin@ is special? If so, is there a way around the problem?