[Mimedefang] Re: Great open letter about anti-virus, emails, bounces, etc.

[Michael Sims]

mimedefang-admin at lists.roaringpenguin.com wrote:
> It is amazing how much spam stops once you only accept aol.com,
> yahoo.com, etc. mail from hosts which reverse resolve to something in
> those domains. This does require some maintenance, as some places
> outsource some of their mail (e.g. att.com) and sometimes some place
> will switch to a new relay that doesn't have a PTR record in DNS.

I'm curious, since I would love to put something like this into place.  (It
seems that here lately the amount of spam from dial-up/dynamic accounts has
skyrocketed).  In the examples you give (outsourced mail, and relays without
PTR records), how did you know about the problem?  I mean, if you're
rejecting mail on this basis, how did you know that some of it was legit?
Did someone contact you through some other means?

I'm seriously considering setting up a blacklist like this where I can tell
relays with PTR records like...

/ip.*\.suscom\.net/
/pcp.*\.comcast\.net/
/.*ppp.*\.tiscali\.no/
/([0-9]{1,3}-){3}[0-9]{1,3}\..*\.rr.com/
/([0-9]{1,3}-){3}[0-9]{1,3}\.client\.insightBB\.com/
/([0-9]{1,3}-){3}[0-9]{1,3}\.client\.attbi\.com/

...to go away and use their ISP's mail relay to send their mail.  I'm afraid
if I do this that I'll run across some fly-by-night company that's too cheap
to get a decent hosting solution and is trying to run a business off a
residential dynamic connection.  And it'll be my luck that this will be a
client that one of my end users will swear they need to do business with.

I'm thinking about giving them a custom rejection message with a URL
pointing to an explanation and a web form they can use to email postmaster,
but I'm not sure if that'll be enough to keep my superiors off my case if
that ever happens...sigh...

___________________________________________
Michael Sims
Project Analyst - Information Technology
Crye-Leike Realtors
Office: (901)758-5648  Pager: (901)769-3722
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