Hi,
I'm facing a strange issue that I never saw before.
I have to relay an email with a big size (>20MB). My postfix server is
accepting emails with a size up to 50Mo, so I did received this email.
However, the server to which I need to send the email only accept message
with a size lower than 12MB.
Usually postfix detect this after the EHLO command and just end the
communication before sending a bounce to the sender.
But in my case, postfix is sending the email anyway untill the remote server
send an error "552 Data size exceeded". When it does that, postfix doesn't
see it and we can see TCP retransmit of the last TCP segment untill there is
a timeout.
I end up with this error in my log file:
dsn=4.4.2, status=deferred (conversation with XXXXX [XX.XX.XX.XX] timed out
while sending message body)
Here is the email in postqueue :
8CA2E5EFD9 25397994 Thu Sep 28 16:30:17 XXXXX@XXXXX
(lost connection with XXXXX [XX.XX.XX.XX] while sending message body)
XXXXX
You can see the size of 25397994 bytes (24MB)
Here is the begining of the SMTP exchange :
220 SMTP Welcome
EHLO XXXXXXXXXXXX
250-SIZE 12582912
250-DSN
250-ENHANCEDSTATUSCODES
250-AUTH NTLM
250-8BITMIME
250 OK
MAIL FROM:<XXXXXXX@XXX>
250 2.1.0 Sender OK
RCPT TO:<XXXX@XXXX> ORCPT=rfc822;XXX@XXXX
250 2.1.5 Recipient OK
DATA
354 Start mail input; end with <CRLF>.<CRLF>
You can see the "250-SIZE 12582912" which means the server only accept
emails of less than 12MB.
However, postfix continue to send the email.
And finally, you can see below a screenshot of a wireshark capture where we
see the TCP retransmissions.
<http://postfix.1071664.n5.nabble.com/file/t6668/capture.png>
I am running postfix version 2.11.0 :
# postconf -d | grep mail_version
mail_version = 2.11.0
Thank you
--
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