mailing list archives
Re: smtp.comcast.net self-signed certs
From: Jeff Mitchell <jeff () emailgoeshere com>
Date: Fri, 16 Jan 2009 11:39:51 -0500
Tony Finch wrote:
My understanding is that Comcast uses it simply for encryption, not for
That's not entirely true. SMTP over TLS is intended to work for
inter-domain SMTP, and it is in fact quite frequently used.
You're right; certificate verification was turned on on my end simply
because I'd never had a reason to turn it off (since in recent times the
majority of my mail goes through their gateway, which has never
presented an invalid certificate to me before).
* Most SMTP software does not check certificates and many certificates
installed on MX hosts have different common names from the MX record
target hostname. Turning on certificate verification breaks too much
email, and there's no incentive for postmasters to install valid
However, in this case, there is another benefit: the presence of what
was clearly a default certificate on some of their servers, where before
there were always valid certificates presented, could indicate that the
rest of the mailserver was incorrectly configured. Better that mail is
delayed than it is accepted and ends up bounced or disappearing into
the ether (that was my main incentive for the OP) :-)
FWIW, this seems to be fixed today.