>This problem seems to have cropped up after sendmail ( Solaris 5.3 ) had been
>installed on our remote site, and had been working just fine for a month or
>The symptoms are the following :
> (a) We get the following errors on the console window of the mailhost :
> SYSERR: net hang reading from <some host>
> Connection timed out during mail with <some host>
> As a result of this, a lot of mail does not get to/from our remote site.
important one. You might even want to ioncrease the number further
(to two hours).
You probably also want to cut down the number of sendmail processes.
The best way to this is to have sendmail queue all the mail and deliver
it only on the queue runs (Odq).
4.11) TCP/IP connections time out too soon, especially on slow links.
The tcp/ip abort interval in Solaris 2.x is too short,
the default value is 2 minutes. The result is that when an
ACK isn't received in *2* minutes, the connection is closed.
This is most often seen by sendmail, which will log
sendmail: SYSERR: collect: read timeout on connection from ...
You can fix this by running following command (e.g., at boot),
which increases the timeout to 20 minutes (unit is millisec).
/usr/sbin/ndd -set /dev/tcp tcp_ip_abort_interval 1200000
4.12) Solaris 2.x can't set up any TCP/IP connections to certain hosts.
Solaris 2.x sets the don't fragment bit on all packets it send
as part of MTU path discovery. The Solaris 2.x implementation
is RFC compliant, but the MTU path discovery protocol will
fail when there are broken routers in the path.
Typical symptom is not being able to connect from a
Solaris 2.x hosts but having no trouble from other hosts.
/usr/sbin/ndd -set /dev/ip ip_path_mtu_discovery 0
--- end of excerpt from the FAQ
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