MV.COM policy: Mail blocking

MV.COM policy: Mail blocking

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The MV Communications policy towards blocking mail has always been pretty easy to express, with these two tenets:

  1. We would rather not block any mail, preferring to leave that decision up to each individual mailbox owner;

  2. 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:

    1. 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.

    2. 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.

    3. 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.

    4. 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, Sun Jun 22 13:30:38 EDT 2008. When looking at the lists that follow, bear in mind:

     

    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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