[Mailman-Users] Comcast, Yahoo, Hotmail blocking us

[Brad Knowles]

On 9/1/07, Mark Sapiro wrote:

>  I suppose that's possible, but before going down that road, I would
>  make sure that the domain that the server identifies itself as in SMTP
>  HELO or EHLO is the same domain returned by an rDNS lookup of its IP
>  address.

Another factor might be the firewall.  Some firewalls (especially 
certain versions of the Cisco PIX) are known to break SMTP in some 
pretty horrible ways, and it is entirely possible that large sites 
might set up their servers to look for certain types of behaviour 
that are in violation of the protocol.

Or maybe they had these problems previously, and then instituted a 
way to work around them.  But when the firewall changed, they didn't 
un-break whatever else they had to break in a different way, in order 
to work around the previous bizarre Cisco PIX problems.

At the very least, this would be something else to check out.

-- 
Brad Knowles <brad at shub-internet.org>
LinkedIn Profile: <http://tinyurl.com/y8kpxu>