TCP/IP: Operation Timed Out

[yo _]

Hello All!

I manage a general mail server for my organization and recently i have been 
receiving complaints that not all their messages are being sent. A quick 
check to the maillog and i noticed that many of the mail servers of the 
receivers are getting "Operation timed out" responses. I manually checked 
connecting to these servers using telnet to see if it was just my mta, but 
to my surprise telnet was unable to connect as well!

At home i tried connecting to these servers via telnet on port 25 as well, 
and it worked with ease. Then immediatly I ssh'ed to our remote mail server 
and telnet'ed to these "operation timed out" mail servers on port 25 and 
still same thing. Now this shocked me, how could i be easily connecting to 
the mail servers from home, and from the location of our mail server, not be 
able to. It connects to other mail servers there are just a few that do not 
work including:

smtp1.dadeschools.net
mail1.dadeschools.net
oitmail.dade.k12.fl.us
sbabmail.dade.k12.fl.us
7841exch2.tecmiami.com

It's not a DNS problem as the dns resolves the same ip address from home and 
where the server resides. I'm not sure if it is solely our mail server or it 
is all the computers on our LAN that are unable to connect, i willl have to 
examine this when i get there sometime this week. The mail server is 
connected directly to the internet and is assigned a public ip address (it 
is not behind a router filewall or is not forwarded packets through NAT). 
The host address of our mail server is mail.e-equality.org.

Does anyone know the nature of this problem or how to solve it? Could it be 
faulty design of the network route from our mail server to theirs? Or maybe 
our TTL settings on the packets are too small.
-Rian Hunter

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