MX problems

Tue May 19 23:19:48 UTC 2009

Polar Humenn wrote:
> I'm in Syracuse NY, and I'm having problems getting sendmail to get to MX
> servers, with the errors of "No Route to Host" or "Connection timed Out".
> Apparently this is been happening for over 5 days. I can send mail within
> Syracuse University, but as soon as I venture out nothing. Traceroute seems
> to loose it after about the 9 or 10th hop.
> 
> It seems that I can get to almost any website, but tracerouting or pinging
> these MX servers is not happening.
> 
> Is there anything going on, or at least something that started 5-7 days ago?
> 
> I find the same problem from within Syracuse Univeristy to my RoadRunner
> account at home (which does not pass through the university routers). I only
> noticed it from the university since thats where I usually send my email
> through. Like I would no have been able to post to this list

Many ISPs, especially for residential and similar customers, filter TCP 
25 outbound and provide a "smart host" MTA on net for their customers to 
use for sending outbound mail.  This is an anti-abuse measure.

If an offnet MX host returns pings but times out when you telnet to port 
25, you're probably being filtered (somewhat) locally.

--
Jay Hennigan - CCIE #7880 - Network Engineering - jay at impulse.net
Impulse Internet Service  -  http://www.impulse.net/
Your local telephone and internet company - 805 884-6323 - WB6RDV