Mailscanner / postfix Timeout in the SMTP dialog

[Fabien GARZIANO]

Hi people !

I think this might not be the right place to ask for this, as it seems
more like a postfix issue. But that's driving me mad.
I got this mail relay : 
Running on
Linux califw3.caliseo.fr 2.6.16-1.2108_FC4 #1 Thu May 4 23:52:01 EDT
2006 i686 i686 i386 GNU/Linux
This is Fedora Core release 4 (Stentz)
This is Perl version 5.008006 (5.8.6)

This is MailScanner version 4.53.8

And postfix 2.2.2

Some time ago, I found that some of the incoming SMTP connections were
interrupted with this kind of message : 
postfix/smtpd[12529]: timeout after DATA from host.domain.ext[x.x.x.x]

And this seems more and more frequent. Some googling drove me to some
MTU or network troubleshoot which didn't solve anything (I've tried to
lower MTU or even to raise it, the server is in a DMZ behind a FW and
next is the ISP router).
I've checked everything outside the mail server (Firewall, network) but
I came to the conclusion that the problem was coming for the server.

Once again, I know this might not be the right place for what I guess is
a pure Postfix issue (as it happens during SMTP exchange), but if anyone
here have experienced the same behaviour, I would be happy to hear about
it.

I also guess I'll have to update the whole server cause it's now quite
old (postfix, MailScanner, etc...).

Thanks.