Wietse Venema:
> Giuseppe De Nicolo':
> > On 09/18/2014 05:40 PM, Wietse Venema wrote:
> > > Giuseppe De Nicolo':
> > >
> > >> 136.231890 217.72.32.234 212.19.117.109 SMTP 227 C:
> > >> MAIL FROM:<giampaolo.marcol...@bertoliniassociati.it> SIZE=2857 |
> > >> RCPT TO:<giulio.digior...@oapointgroup.it>
> > >> ORCPT=rfc822;giulio.digior...@oapointgroup.it | DATA
> > >> 136.233724 212.19.117.109 217.72.32.234 SMTP 131 S:
> > >> 250 2.1.0 Ok | 250 2.1.5 Ok | 354 End data with <CR><LF>.<CR><LF>
> > >> 136.441076 212.19.117.109 217.72.32.234 SMTP 131 [TCP
> > >> Retransmission] S: 250 2.1.0 Ok | 250 2.1.5 Ok | 354 End data with
> > >> <CR><LF>.<CR><LF>
>
> There is another possibility.
>
> The SMTP client sends MAIL FROM/RCPT TO/DATA as one request
> (SMTP command pipelining, RFC 2920), that's why Postfix replies
> with 250/250/354 as one response.
>
> It is possible that there is a device in the path that tries to
> read SMTP conversation and that drops packets it does not understand.
> Stuff like that tends to be built into a network firewall.
Or worse, the device sees the MAIL FROM part and ignores the rest,
then the device sees the first 250 part and ignores the rest. Then
the remote SMTP client starts sending the message but the device
is still waiting for RCPT TO commands, so it drops everything it
does not expect.
> In that case, see what happens when you configure
>
> # postconf -e 'smtpd_discard_ehlo_keywords=pipelining'
> # postfix reload
>
> If that solves the problem then you can make this selective per
> client IP address with smtpd_discard_ehlo_keyword_address_maps.
That would still solve the problem if it is due to a device
that does not understand RFC 2920 command pipelining.
Wietse
