[CentOS] Sendmail and pmtu discovery

Kai Schaetzl wrote:
> Sean Carolan wrote on Tue, 14 Oct 2008 08:13:34 -0500:
> 
> > My mail logs are showing that customers who specifically disallow ICMP
> > traffic have many "Connection Reset" entries in our logs:
> 
> Could somebody explain why ICMP might play a role in mail delivery?

If you don't know the smallest MTU on the path to the mail server, you
might not be able to send packets over that path, especially if DF is
set.

Ralph
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