Why does this always happen to me...
I was looking to leave my IMail/Declude setup as my gateway spam
blocking component, and move hosted E-mail to a different server. All I
needed in the hosted mail server was something that could be configured
in such a way as to only accept SMTP AUTH E-mail or E-mail that only
came from my own gateway. I figured that SmarterMail with port 587
support (the SMTP submission port) would do the trick.
Well, it turns out that despite earlier claims, SmarterMail supports
another SMTP port of your choosing, but it doesn't limit it to SMTP
AUTH-only. This means that the spammers that have a habit of bypassing
your MX records for indefinite periods of time will be able to still hit
the SmarterMail server and bypass the scanning gateways. I found a post
from two days ago that pointed out this major shortcoming, and despite
an earlier thread on the topic, it turns out that this is a real limitation.
I started searching for alternative methods around this, such as setting
up a custom zone that blacklists the whole Internet except for the IP
space of my scanning servers and using their internal spam blocking to
delete anything that didn't come from my own space or was AUTHed. I ran
into another problem here however...their blacklist capabilities don't
allow for unique result codes, so anything that returns a result from a
blacklist is treated as a positive hit. I had to actually create a
CNAME record for a bogus domain to correspond to this space in order to
work around that limitation and it worked. I then however figured out
that they do not whitelist based on SMTP AUTH, but instead, they
whitelist anything with a local address, and if a user doesn't have a
local address in their headers but still AUTH's, it won't be
whitelisted. So due to this shortsighted implementation on multiple
fronts, there is no practical way to accomplish this and have it be
reliable.
I also came across another thread while researching things where some
fellow Declude users were pointing out how their gateway configuration
affected blacklists. We all know here that when gatewaying through a
different server, you need something that is the equivalent of IPBYPASS
for the gateway. They overlooked this, and after it was pointed out to
them they suggested that they instead test all hops, which would have
resulted in tagging many messages that are sent from clients on DUL IP
space. I'm not sure that by the end of the thread that the concept
stuck with them.
It is a very pretty application, but it has a lot of settings within it
and a few of them don't seem very well thought out. I E-mailed their
tech support asking for ways around this or an indication of plans to
support AUTH-only on the SMTP submission port and they ducked the
questions saying that it wasn't possible to do at this time and directed
my ticket to their sales staff so that I could get a refund.
Unfortunately they seem to need to create a functional whitelisting
mechanism for AUTHed users also for this to work instead of one based on
the Mail From address. I'm a little put off by the short answers in
response to such things, and the rubber stamped reply that it will be
added to their suggestion database. Maybe I'm expecting too much...
At this point, I'm looking for alternatives...including using IMail on
the new server (I can do this with 8.20). I am also hopeful that
maybe some of the others around here have run into this issue and
possibly have some alternative suggestions. While I don't want to
support IMail any longer and feel that they might again pull the rug out
from under me, I can migrate things in a snap and I won't have to worry
about taking a risk with SmarterMail.
Matt
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MailPure custom filters for Declude JunkMail Pro.
http://www.mailpure.com/software/
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