broken pipe

I keep getting stuck messages. This is 0.56 hpux9.05.

It seems that all these failures are when a large message is being
delivered to a remote gateway. This gateway is running:

220 smtpgw.cws.comsat.com IMA SMTP 2.03 (Beta 5) Enterprise Server 001957 ready at Fri Oct 18 13:23:53 1996

It fails saying "broken pipe".

Any ideas?