On 2008-11-12 17:53, Sean Walberg wrote:
On Wed, Nov 12, 2008 at 5:16 PM, Gilbert E. Detillieux <gedetil@cs.umanitoba.ca mailto:gedetil@cs.umanitoba.ca> wrote:
> 451 4.5.0 SMTP protocol violation see RFC 2821 Usually, an error message like that would suggest something is messed up in the MTA configuration at one end or the other. Did you bother to check this site for likely possibilities?... http://www.rfc-ignorant.org/rfcs/rfc2821.phpWhich one of the 79 pages do you suggest he starts with, Gilbert?
Actually, I was thinking of the 5 or 6 colour-highlighted passages within the page, corresponding to the conveniently-indexed sections listed right at the top of the page, which point to some of the more likely issues to be encountered with misconfigured MTA's.
But it looks like none of those were particularly relevant in this case...
While you're mulling that over, I'll suggest something more helpful:
http://forums.devshed.com/mail-server-help-111/gmail-responds-451-4-5-0-smtp...
Google's the one at fault here, the thread has a workaround from the postfix mailing list, and seems to have fixed the problem permanently.
See also: http://www.spamresource.com/2008/11/gmail-tempfailing.html
While browsing this site today, for totally different information, I came across that entry. Looks like sites running "an MTA that utilizes pipelining aggressively" (Postfix is a likely one) are running into this. John, if the problem went away without you changing anything at your end, it's possible Gmail tweaked something in response to complaints from others.