[CentOS] Sendmail and pmtu discovery

Kai Schaetzl wrote:
> 
>> 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?

It is required for any TCP conversation, unless as a matter of luck you 
happen to have the same MTU capability across the whole path - or the 
end points restrict their MTUs arbitrarily to a size that everything can 
handle.

-- 
   Les Mikesell
    lesmikesell at gmail.com