[Top] [All Lists]

After a 450, queue or try next MX?

2006-08-30 08:24:06
I'm having problems sending to a 'greylist'-ing mail host and was wondering
what the correct response to the initial delivery rejection ought to be. I
was not able to find the answer in the RFCs. I was hoping someone here might

When we attempt to deliver to the recipient, the first of two hosts
listed MX preference order responds with a 450
From our log, (IP and address obfuscated)

Remote host: 99.99.999.999. RCPT response: '450 <xxx(_at_)xxxxxx(_dot_)net>: 
address rejected: Greylisted for 300 seconds (see

'. Trying next host.

When we try the next host we get this:

Remote host: 33.333.333.333. Recipient: '<xxx(_at_)xxxxx(_dot_)net>'. RCPT 
'554 xxx(_at_)xxxxx(_dot_)net: Relay access denied

At this point a delivery failure with the 554 is returned to my sender.

When I contacted the admin at the recipients domain he asserted that my mail
server was misconfigured, and that we should be retying. While I'm not going
to say that is not the case, I'm trying to figure out first what it is that
should happen here.

After the inital temporary failure, the 450, should my mail server
immediately put the message in the retry queue, or should it try the next MX
host? And if it should try the next MX host, should it then return the
permanent failure that second host gave me, or put the message in retry
because the first host attempted returned a temporary rejection?

My mail server is trying the second MX and then returning the permanent
failure to the user.

Sorry if this is complicated or too basic. I just have not been able to find
the description of this scenario in the RFCs.


<Prev in Thread] Current Thread [Next in Thread>