Sean Wallbridge
5.7.1 is the hardest to troubleshoot I find (take my experience with a grain of salt). In fact, most times I see this particular one, it is that the server you were trying to deliver to, had problems. I’ve seen…
1. The server was in a midservice startup and rejected, temporarily, any new connections, throwing back a 5.7.1 until it was finished starting up
2. They are having bigger problems, and rejected for any number of reasons
3. I *believe* that sometimes, some mailservers use this as their default response when they are rejecting the sender server (AIDPs). The 5.7.1 response is kind of a lie, and in fact, they are rejecting because AIDP is on a black list (doubtful) on an untrusted subnet (like Shaw) or perhaps even a bogus PTR record
So, check the domain (aidp) for dnsstuff.com test, health on mxtoolbox.com and from the Exchange Server, telnet to their mail server (find out which one via nslookup) and see if it rejects your SMTP connection (won’t stay open or show a greeting) or perhaps it spits back saying it doesn’t like your reverse lookup match.
More…
5.7.1: Possible causes:
1)General access denied, sender access denied – the sender of the message does not have the privileges required to complete delivery.
2)You are trying to relay your mail through another SMTP server and it does not permit you to relay.
3)The recipient might have mailbox delivery restrictions enabled. For example, a recipient’s mailbox delivery restriction was set to receive from a distribution group only and non-members’ e-mail will be rejected with this error.
4)For Exchange Server 2003, a distribution group can be configured to restrict mail delivery from unauthenticated users. Mail that is sent by using an unauthenticated SMTP session are rejected.