Kurt Bigler wrote: <snip>
The plot thickens. sockstat produced no output, apparently a limitation of the virtual server implementation. Inquiring into this, the parent server apparently had default processes answering (stupidly) when virtual server email servers were not running. The administrator fixed this with a quick configuration change, and now everything behaves as expected.
Thanks for your help, which lead to the resolution. Still a mystery to me why a default SMTP answerer would respond with 5.7.1. I inquired about that but got no reply yet.
Well, that is an easy one, if they are running qmail as well, it would answer with a 5.7.1 meaning your domain is not in their rcpthosts.