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How Tuffmail Spam Scoring Works

Tuffmail spam scoring is based on the SpamAssassin(tm) Open Source software. Scoring may be enabled or disabled and score thresholds set for an address, for a domain, or for the account. Allow/Deny lists can be created for an individual address, for a domain, or for the account.

An address or domain entry in an Allow list bypasses spam scoring for senders that send very spammy looking email that is not spam. There is a global Allow list that can be used also. This list contains senders that are truly confirmed opt-in advertisers that send email that looks just like spam.

An address or domain in a Deny list tags the email with an X-Spam-Discard header. Email delivered to a Tuffmail mailbox stores email with this header in the Discard folder. Discard folders are automatically purged every 5 days.

There are two user configurable scoring thresholds. Email scoring at or above the first threshold can be tagged with an X-Spam-Junkmail header and/or the subject can be tagged with a prefix of your choice. Email delivered to a Tuffmail mailbox stores email tagged with this header in the Junkmail folder. The Junkmail folder is automatically purged every 30 days.

Email scoring at or above the second threshold will be tagged with an X-Spam-Discard header. Email delivered to a Tuffmail mailbox stores email with this header in the Discard folder. Discard folders are automatically purged every 5 days.

Scoring occurs before the final destination of the email is determined. Email forwarded to a server outside the Tuffmail system can use the headers to determine what to do with the email.

The average spam score is currently 13 with 95% of the spam scoring 5 or higher. 99% of the spam scores 4 or higher. 99.9% of the non-spam email we see scores 4 or lower. This does not include requested newsletters full of web bugs, unsubscribe links, and special offers that look just like spam. The average non-spam score is -5. Most all person to person email will score below 0.

The default thresholds are 6 and 13 and depending on what kind of spam you are receiving and what newsletters you are subscribed to, these settings will deliver almost all spam to the Junkmail or Discard folder. Better results are achieved by adding newsletter senders to an Allow list and setting the thresholds a bit lower.

The scoring results are added to the email headers when scoring is enabled for an address or when we are sending all email through the scoring system for testing. When testing, scoring headers are added but the email is delivered as it would be if you have scoring disabled. Scoring headers look like this:
X-Spam-Status: Yes, score=28.7 threshold=5.0
X-Spam-Report: Content Analysis details:
 1.3 X_PRIORITY_HIGH        Sent with 'X-Priority' set to high
 2.7 SUBJ_YOUR_FAMILY       Subject contains "Your Family"
 0.6 TO_MALFORMED           To: has a malformed address
 4.1 MSGID_SPAM_ZEROES      Spam tool Message-Id: (12-zeroes variant)
 0.5 X_MSMAIL_PRIORITY_HIGH Sent with 'X-Msmail-Priority' set to high
 1.2 HTML_IMAGE_ONLY_02     BODY: HTML: images with 0-200 bytes of words
 2.0 MIME_HTML_ONLY         BODY: Message only has text/html MIME parts
 5.4 BAYES_99               BODY: Bayesian spam probability is 99 to 100%
 [score: 0.9996]  0.1 HTML_MESSAGE         BODY: HTML included in message
 2.2 HIDE_WIN_STATUS        BODY: Javascript to hide URLs in browser
 4.1 MSGID_OUTLOOK_INVALID  Message-Id is fake (in Outlook Express format)
 2.5 RCVD_IN_DSBL           RBL: Received via a relay in list.dsbl.org
 [<http://dsbl.org/listing?ip=80.202.114.125>]
 1.0 FORGED_OUTLOOK_TAGS    Outlook can't send HTML in this format
 1.0 FORGED_OUTLOOK_HTML    Outlook can't send HTML message only
X-Spam-Check: Enabled
X-Spam-Discard: Yes
X-Spam-Score: 28.7
X-Spam-Flag: Yes

Examining the scoring headers can help you determine what scoring thresholds to use.