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sender_reputation = txrep_weight_email_ip * email_ip_reputation +
txrep_weight_email * email_reputation +
txrep_weight_domain * domain_reputation +
txrep_weight_ip * ip_reputation +
txrep_weight_helo * helo_reputation
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The default values of the weight factors:
- txrep_weight_email_ip = 10 (of total 19.5, hence 51%)
- txrep_weight_email = 3 (of total 19.5, hence 15%)
- txrep_weight_domain = 2 (of total 19.5, hence 10%)
- txrep_weight_ip = 4 (of total 19.5, hence 21%)
- txrep_weight_helo = 0.5 (of total 19.5, hence 3%)
Depending on configuration, TxRep uses either a global storage to keep the reputation record (same for all users), or a User storage (a separate storage for each user ID that can run SpamAssassin). Alternatively, when the txrep_user2global_ratio is enabled, both storages are used concurrently. When both storages are used, each of the two reputations are calculated in the same way as shown above, using sender values from the respective storages (when available), and ten the overall reputation is calculated with the following formula:
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total reputation = ( txrep_user2global_ratio * user + global ) / ( txrep_user2global_ratio + 1 ) |
The default value of txrep_user2global_ratio is 0 (dual storage disabled). The setting takes values between 0 and 10. The value around 2 may be a good starting point when enabling the feature (user storage reputation has twice the weight of the global reputation). Before enabling the dual storage, make sure your system is configured to call SpamAssassin under the respective user id. In many installations, SA is always called with the same user id. In such cases, activating the dual storage would be useless.
The overall txrep_factor can be adjusted in the configuration to adjust the impact of the reputation, which may be useful when starting off. The value of the corrective TXREP tag is calculated in the following way:
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corrected score = current score + txrep_factor * (reputation + current score)/(count+1) TXREP tag value = corrected score - current score |
The default value of the txrep_factor is 0.5, but unlike at AWL, the final result is also depending on the count of recorded messages of given sender. In the result, the factor of 0.5 is equivalent to the AWL factor of 0.25 at senders with one record, and its influence rises close to the projected value of 0.5 logarithmically with the number of sender messages recorded.
Additionally to the algorithms shown above, the reputation is also influenced by the
txrep_dilution_factor. This factor was introduced to help wearing out the influence of old records. When the factor is used, the new score will always have a slightly higher weight than the stored values. It means that the influence of old records progressively drops with each new message from the sender. The formula below is used:
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newtotal = (oldcount + 1) * (newscore + txrep_dilution_factor * oldtotal) / (txrep_dilution_factor * oldcount + 1) |
The default value of the txrep_dilution_factor is 0.98, and it takes values between 0.7 (fast dilution / expiry), and 1.0 (no dilution at all).
The schema txrep-diagram.gif demonstrates the calculation of the TXREP tag value.
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