Greetings:

I decided to upgrade one of my e-mail servers from NetBSD 1.62 to
NetBSD 3.0_RC5.  Everything seems to work with one exception, and
that is sendmail.

Specifically, many of the incoming messages hang and timeout,
with the following error message:

  451 4.4.1 timeout waiting for input during message collect (held)
  421 4.4.1 gate1.engine.ca Lost input channel from mail.bubo.net

This looks like a Path MTU Discovery issue, since the external
interface only has an MTU of 1460.

However, I allow all related ICMP packets to pass through in my
IPFILTER config:

  pass in  quick proto icmp from any to any icmp-type 3 code 4
  pass out quick proto icmp from any to any icmp-type 3 code 4

Much of the configuration in the new NetBSD 3.0_RC5 is identical
to the previous NetBSD 1.62, so I am at a loss as to why my
incoming e-mail is timing out.

Any suggestions are greatly appreciated.
Thank you in advance,
Alicia.