Spam Filtering

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Spam Filtering

SpamAssassin at XMission

XMission offers a very effective strategy to identify unsolicited email sent to our customers on all of our email platforms. While XMission has been blocking spam for years, this spam identification software is catching a large percentage of the mail that gets past preexisting spam filters.

The spam detection software is called "SpamAssassin" and it scans incoming email for various characteristics that are often found in spam messages. Anything from keywords, to file types. Each of these characteristic gets a certain number of points, which are then added together to determine the likelihood that a message is spam. By default, SpamAssassin considers anything with a score of 5 or higher as spam but in our tests some legitimate email can get tagged higher than 5. This is why we've chosen a slightly higher, but safe, number of 8. Know that we are careful to avoid marking or tossing legitimate email destined for our customers.

The headers that SpamAssassin adds to your email messages looks something like this:

    X-Spam-Status: No, score=6.9 required=8.0 tests=NO_REAL_NAME,PLING,PLING_PLING,HT
    X-Spam-Level: ******

  • The X-Spam-Status header shows whether or not the message scored high enough to be considered spam, what the actual score was, what's required for it to be qualified as spam, and what tests/characteristics were positive. The X-Spam-Level header shows the whole number score with asterisks. A message with a score of 6.9 would show 6 asterisks
  • If the message reaches the score required to be considered spam, the following header is added:
    X-Spam-Flag: YES
  • By default the XMission system will set the X-Spam-Flag to YES on 8 or higher
  • Users could filter with "X-Spam-Flag: YES"
  • Users can also adjust level of filtering by using X-Spam-Level "contains" "*******" (or whatever amount of stars)

You may also choose to filter, or sort messages yourself. Unfortunately, most commercial email clients don't support special headers.

NOTE: Though this is the best spam detection software we've encountered, it is not foolproof. There is a small chance some legitimate email might be incorrectly identified as spam. Use this service at your own risk.


For assistance on creating custom spam filters for '' accounts, please refer to Webmail_Spam_Filtering


For assistance on creating custom spam filters for your hosted Zimbra domain accounts, please see Zimbra_Base_Spam_Filtering