Strange hanging of zmailer

[Andras Micsik <micsik@sztaki.hu>]

Hi, 

We are using zmailer 2.99.51-pre2 with Solaris 7. Generally it forwards
messages almost instantly, but with some hosts (mostly with a NextStep)
very often mails get stuck for an hour on the server. I found a strange
situation, which may be the cause of this. zmailer regularly hangs for
some minutes while sending a message. Here is a network trace of what
happens:

receiver -> sender       SMTP R port=44756
      sender -> receiver SMTP C port=44723 MAIL From:<micsik@sender
receiver -> sender       SMTP R port=44723
receiver -> sender       SMTP R port=44723 250 <micsik@sender
      sender -> receiver SMTP C port=44723 RCPT To:<micsik@receiver
receiver -> sender       SMTP R port=44723 250 <micsik@receiver
      sender -> receiver SMTP C port=44723 DATA\r\n
receiver -> sender       SMTP R port=44723 354 Enter mail, end
      sender -> receiver SMTP C port=44723 Received: (from loca
receiver -> sender       SMTP R port=44723 250 Ok\r\n
      sender -> receiver SMTP C port=44723

... and then nothing happens for several minutes.
The scheduler logs:

20000112172711 DBGdiag: # smtpclient:20935: bytesleft: 1
20000112172711 DBGdiag: # smtpclient:20935: Premature EOF in Z/141725-219!
20000112172711 DBGdiag: # smtpclient:20935: Truncated or illegal control
file "Z/141725-219"!
Resyncing file "Z/141725-219" (ino=141725) (of=1 ho='receiver') ..
resynced!

What can I do against this?

-----------------------------------------------------------
  Andras Micsik              micsik@sztaki.hu
  MTA SZTAKI Hungary         http://www.sztaki.hu/~micsik