'571 Mail Relay Is Not Allowed' error

[E-Double]

For some reason, several Outlook 2003 users keep receiving the following
error message when sending emails: "The Following Recipients Could Not Be
Reached, (e-mail address removed) on 09/29/2006 2:44PM, 571 Mail Relay Is Not
Allowed." This is when sending emails thru the regular, local email server
and to known users in the address book. The error message pops-up
immediately when trying to send, seemingly before it would have time to even
attempt to hit the remote or even local email servers. These errors just
started about three or four weeks ago with the few Outlook users but never
seem to occur with the Outlook Express users. TIA for any help on this one.

 

[John Bailo]

For some reason, several Outlook 2003 users keep receiving the following
error message when sending emails: "The Following Recipients Could Not Be
Reached, (e-mail address removed) on 09/29/2006 2:44PM, 571 Mail Relay Is Not
Allowed." This is when sending emails thru the regular, local email server
and to known users in the address book. The error message pops-up
immediately when trying to send, seemingly before it would have time to even
attempt to hit the remote or even local email servers. These errors just
started about three or four weeks ago with the few Outlook users but never
seem to occur with the Outlook Express users. TIA for any help on this one.

I've been seeing more of these messages in my sendmail logs. The cause
almost always is the use of a Postini spam filter. They use the 571 as
their error response when blocking a domain or email sender.