mail greylisting and SMTP status codes
Hi Experts
I have a forwarding mailserver inside my office (sendmail) which does some virus check on outgoing mail.
All goes fine except with a particular domain, which always rejects my mails. I spoke with the maintainer of that domain and he says his mailserver is rejecting mails because it is doing greylisting.
But mails are rejected with errors like 5xx which I know are permanent failures.
I assert that his mailserver should return an error like 4xx for greylisting.
He replies that my mailserver is misconfigured and should keep retrying after the first 5xx error.
Who's right and who's wrong?
And, if I'm wrong, can someone point me out on how to configure sendmail to retry sending after the first 5xx error?
I have a forwarding mailserver inside my office (sendmail) which does some virus check on outgoing mail.
All goes fine except with a particular domain, which always rejects my mails. I spoke with the maintainer of that domain and he says his mailserver is rejecting mails because it is doing greylisting.
But mails are rejected with errors like 5xx which I know are permanent failures.
I assert that his mailserver should return an error like 4xx for greylisting.
He replies that my mailserver is misconfigured and should keep retrying after the first 5xx error.
Who's right and who's wrong?
And, if I'm wrong, can someone point me out on how to configure sendmail to retry sending after the first 5xx error?
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ASKER
Oh thank you noci. I much appreciate your opinion. Unfortunately there is plenty of buggy and badly configured software out there.
So now I must convince this person that he is wrong and that he'd better review his config --
No more opinions needed, RFC says it all - closing Q.
So now I must convince this person that he is wrong and that he'd better review his config --
No more opinions needed, RFC says it all - closing Q.
ASKER
I had a look at the various RFCs and that shed some light on the problem.
Now, one more little question before closing this Q.
The receiver is, obviously, badly configured. But if I use e.g. gmail SMTP server, emails are delivered.
Does this mean, in your opinion, that gmail itself is violating RFC, in an effort to deliver mail to buggy SMTP servers?