When an email message is marked as spam it can be useful to know which criteria were triggered.
The following example shows exactly why the message got a spam score of 6.457:
X-Spam-Flag: YES
X-Spam-Score: 6.457
X-Spam-Level: ******
X-Spam-Status: Yes, score=6.457 tag=2 tag2=6.31 kill=6.31
tests=[BAYES_00=-1.9, HTML_IMAGE_ONLY_24=1.618, HTML_MESSAGE=0.001,
HTML_MIME_NO_HTML_TAG=0.377, MIME_HTML_ONLY=0.723,
NO_DNS_FOR_FROM=0.001, RCVD_IN_PBL=3.335, RCVD_IN_RP_RNBL=1.31,
RDNS_DYNAMIC=0.982, T_REMOTE_IMAGE=0.01] autolearn=no
X-Spam-Report:
* 1.3 RCVD_IN_RP_RNBL RBL: Relay in RNBL,
* https://senderscore.org/blacklistlookup/
* [1.2.3.4 listed in bl.score.senderscore.com]
* 3.3 RCVD_IN_PBL RBL: Received via a relay in Spamhaus PBL
* [1.2.3.4 listed in zen.spamhaus.org]
* 0.0 NO_DNS_FOR_FROM DNS: Envelope sender has no MX or A DNS records
* -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1%
* [score: 0.0000]
* 1.6 HTML_IMAGE_ONLY_24 BODY: HTML: images with 2000-2400 bytes of words
* 0.0 HTML_MESSAGE BODY: HTML included in message
* 0.7 MIME_HTML_ONLY BODY: Message only has text/html MIME parts
* 0.4 HTML_MIME_NO_HTML_TAG HTML-only message, but there is no HTML tag
* 1.0 RDNS_DYNAMIC Delivered to internal network by host with
* dynamic-looking rDNS
* 0.0 T_REMOTE_IMAGE Message contains an external image
To add this information to the headers of a message you need to edit one of the config files of amavis:
nano /etc/amavis/conf.d/50-user
and add the following lines:
# insert X-Spam-Report header field? default false
$sa_spam_report_header = 1;
Now restart amavis:
service amavis restart