Re: Odd ipfilter/postfix interaction

On Thu, Feb 17, 2005 at 04:20:12PM -0600, David Bogen wrote:

> Then, I tried looking at MTU issues since that is what Googling the
> problem seemed to indicate might help. I tried mucking around with MTU
> settings in /etc/ppp/ppp.conf (since I use PPPoE to connect to my DSL
> provider). No matter how (reasonably) low I set the MTU, the messages
> would not go through.
>

The issue is not the specific MTU value, but rather blocking of the ICMP
messages that signal the need to reduce the MTU.

If you want to lower the MTU, reduce it on the Postfix server, not the
firewall (that merely compounds the problem). It is also possible that
the peer MTA's firewall is equally misconfigured.

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