Not receiving mail from selected domains

[bjwiz]

We are finding that selected vendors/customers (12 so far that we know of)cannot send email to us -- Delivery Failure. We do receive over 1500 emails per day and have no problem sending. If a given domain cannot send it, it ALWAYS gets a failure -- it is not intermitant.

Here is the environment:
Exchange 5.5 running on Windows2000 server
DSL line direct IP addr - outside fire wall
Symantec Enterprise AV for Exchange
Server also runs small IIS web server

There are no addrs in Exch connection filters.
I have spent hours checking to see if we are listed on any spam or blackhole filters -- none.
I have had two customers run TraceR -- stops at my ISP.
A couple of the failures mention DNS unknown.

Any help wizards?

Bill Jack

 

[sicktrick]

ask your IT counterpart if they can do:

telnet billjack.com 25

and see if they get an exchange banner

 

[dennisbbb]

Your isp's router may have died preventing traffic flow from some part of the country. Happens a lot.