Wietse Venema:
> Petr Janda:
> > > If there is a traffic shaper at your end, it may replace your
> > > TCP stack's MSS=1460 announcement by something smaller, like 890.
> >
> > Could this also be caused by the ISP?
>
> Something is throwing away the first 7300 bytes of the email message.
>
> Depending on how pervasive this behavior is, it happens at your
> end, at your ISP, in the middle, at the remote ISP, or at the other
> end. I'll send a 200k email message to postmaster@ and see what's
> up.
Well, mail to postmaster@ bounced (user unknown) but the TCP
handshake shows clear signs of tampering:
19:35:14.389740 168.100.189.2.3865 > 202.76.131.108.25: S
2828872390:2828872390( 0) win 16384 <mss 1460> (DF)
19:35:14.678519 202.76.131.108.25 > 168.100.189.2.3865: S
409513452:409513452(0) ack 2828872391 win 57344 <mss 760>
19:35:14.678556 168.100.189.2.3865 > 202.76.131.108.25: . ack 1
win 16720 (DF)
Can you verify that your machine really announces a MSS of 1460?
Wietse
