But we'll block certain sources in the rare event that those
sources are interfering with our ability to operate.
For most of our corporate life, tenet #1 meant that we didn't block
anybody. However, as the volume of SPAM and what amounts to SPAM
attacks has increased, we have had to bow to pragmatics now and then.
As a result:
- If we receive a particularly high level of mail bombardment that
interferes with our mail servers' operation, we add the source to a block
list, perhaps temporarily, but usually until we receive a request from a
customer to remove that block. This is not brand new: this is a result of
tenet #2. But we are very cautious about this. Over a few years of adding
to this list, we've only accumulated a few dozen entries.
- Starting mid-2003, we have begun to treat a small number of foreign
sources specially, specifically those netblocks that have significant
number of open mail relays used by spammers to hide their tracks.
Usually this special treatment means that we reject individual
sources from those netblocks only if they are on one of
a couple of DNS-based blacklists. This does not affect the
vast majority of sources.
- When under heavy SPAM attack, we may also block or
limit mail from foreign networks observed to be directing huge
amounts of SPAM towards us.
- As of mid-October 2003, we also apply some specialized mail filters
on mail bounces. Our SMTP servers only accept incoming mail for known
valid addresses here, but non-delivery can still happen later, e.g. for
mailbox full problems. Most spam is non-replyable or comes from forged
addresses, and thus shouldn't be replied to. Our delivery agent(s) and
other bounce processing tools attempt to suppress post-SMTP delivery notices
for those cases. (Our main focus is on not accepting those messages in
the first place.)
As we progress in our mail handling and SPAM filtering capabilities,
we expect to be able minimize whatever blocking action we take.
Block lists
These are the lists that are being blocked as of today,
Thu Feb 4 19:33:14 EST 2010.
When looking at the lists that follow, bear in mind:
- An IP address prefix applies to all IP addresses that begin
with the prefix indicated. Thus the prefix "192.168.0."
would apply to "192.168.0.10" but not to "192.168.10.0" .
- A domain name suffix starting with a period applies to any domain name
ending with that suffix. Thus the suffix ".example.com" would
apply to "something.example.com" and to "example.com" itself.
The following sources are being blocked:
We are applying DNSBL selection to the following sources:
If you are an MV customer and you feel that one of these items is
affecting you, please let us know and we will determine how to
proceed.
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