[ale] Blacklisted mail server?

[Bob Toxen]

On Fri, Mar 18, 2005 at 03:28:28PM -0500, Joe Steele wrote:
> On Friday, March 18, 2005 2:54 PM, Nathan J. Underwood wrote:
> >
> > A client of mine has recently started using Cbeyond as their ISP.  Since
> > the cutover, they've had problems sending emails to random domains.
> > After digging around a bit, I've found that they seem to be blacklisted.
> >     The error messages that the users are getting were pretty generic,
> > so I started digging further.  My first move was to ping the server
> > reported as the primary MX for the recipient (got a response).  I then
> > tried to telnet to the mail server (i.e. telnet mail.server.net 25), and
> > got an immediate connection refused.  I then tried the same exercise
> > from my ip (not blacklisted), and was able to connect.  They're not an
> > open relay, and I've not been able to find any lists that their listed
> > on.  Anyone got any suggestions on where to look next?

> Just a guess:

> I believe Cbeyond doesn't usually have reverse DNS set up for their 
> IP addresses.  Could it be that some mail servers are refusing the 
> connection because of this?  If so, then your client can probably 
> report the problem to Cbeyond and have them set up reverse DNS for 
> their IP(s).
This is a distinct possibility.  The turkeys at Comcast use to have
this foobar (no reverse DNS).

> --Joe

Bob Toxen
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