Rspamd
Rspamd is used for AV handling, DKIM signing and SPAM handling. It's a powerful and fast filter system. For a more in-depth documentation on Rspamd please visit its own documentation.
Learn Spam & Ham¶
Rspamd learns mail as spam or ham when you move a message in or out of the junk folder to any mailbox besides trash. This is achieved by using the Sieve plugin "sieve_imapsieve" and parser scripts.
Rspamd also auto-learns mail when a high or low score is detected (see https://rspamd.com/doc/configuration/statistic.html#autolearning). We configured the plugin to keep a sane ratio between spam and ham learns.
The bayes statistics are written to Redis as keys BAYES_HAM and BAYES_SPAM.
Besides bayes, a local fuzzy storage is used to learn recurring patterns in text or images that indicate ham or spam.
You can also use Rspamd's web UI to learn ham and / or spam or to adjust certain settings of Rspamd.
Learn Spam or Ham from existing directory¶
You can use a one-liner to learn mail in plain-text (uncompressed) format:
# Ham
for file in /my/folder/cur/*; do docker exec -i $(docker compose ps -q rspamd-mailcow) rspamc learn_ham < $file; done
# Spam
for file in /my/folder/.Junk/cur/*; do docker exec -i $(docker compose ps -q rspamd-mailcow) rspamc learn_spam < $file; done
Consider attaching a local folder as new volume to rspamd-mailcow in docker compose.yml and learn given files inside the container. This can be used as workaround to parse compressed data with zcat. Example:
for file in /data/old_mail/.Junk/cur/*; do rspamc learn_spam < zcat $file; done
Reset learned data (Bayes, Neural)¶
You need to delete keys in Redis to reset learned data, so create a copy of your Redis database now:
Backup database
# It is better to stop Redis before you copy the file.
cp /var/lib/docker/volumes/mailcowdockerized_redis-vol-1/_data/dump.rdb /root/
Reset Bayes data
docker compose exec redis-mailcow sh -c 'redis-cli --scan --pattern BAYES_* | xargs redis-cli del'
docker compose exec redis-mailcow sh -c 'redis-cli --scan --pattern RS* | xargs redis-cli del'
Reset Neural data
docker compose exec redis-mailcow sh -c 'redis-cli --scan --pattern rn_* | xargs redis-cli del'
Reset Fuzzy data
# We need to enter the redis-cli first:
docker compose exec redis-mailcow redis-cli
# In redis-cli:
127.0.0.1:6379> EVAL "for i, name in ipairs(redis.call('KEYS', ARGV[1])) do redis.call('DEL', name); end" 0 fuzzy*
Info
If redis-cli complains about...
(error) ERR wrong number of arguments for 'del' command
...the key pattern was not found and thus no data is available to delete - it is fine.
CLI tools¶
docker compose exec rspamd-mailcow rspamc --help
docker compose exec rspamd-mailcow rspamadm --help
Disable Greylisting¶
Only messages with a higher score will be considered to be greylisted (soft rejected). It is bad practice to disable greylisting.
You can disable greylisting server-wide by editing:
{mailcow-dir}/data/conf/rspamd/local.d/greylist.conf
Add the line:
enabled = false;
Save the file and restart "rspamd-mailcow": docker compose restart rspamd-mailcow
Spam filter thresholds (global)¶
Each user is able to change their spam rating individually. To define a new server-wide limit, edit data/conf/rspamd/local.d/actions.conf:
reject = 15;
add_header = 8;
greylist = 7;
Save the file and restart "rspamd-mailcow": docker compose restart rspamd-mailcow
Existing settings of users will not be overwritten!
To reset custom defined thresholds, run:
source mailcow.conf
docker compose exec mysql-mailcow mysql -umailcow -p$DBPASS mailcow -e "delete from filterconf where option = 'highspamlevel' or option = 'lowspamlevel';"
# or:
# docker compose exec mysql-mailcow mysql -umailcow -p$DBPASS mailcow -e "delete from filterconf where option = 'highspamlevel' or option = 'lowspamlevel' and object = 'only-this-mailbox@example.org';"
Custom reject messages¶
The default spam reject message can be changed by adding a new file data/conf/rspamd/override.d/worker-proxy.custom.inc with the following content:
reject_message = "My custom reject message";
Save the file and restart Rspamd: docker compose restart rspamd-mailcow.
While the above works for rejected mails with a high spam score, prefilter reject actions will ignore this setting. For these maps, the multimap module in Rspamd needs to be adjusted:
-
Find prefilet reject symbol for which you want change message, to do it run:
grep -R "SYMBOL_YOU_WANT_TO_ADJUST" /opt/mailcow-dockerized/data/conf/rspamd/ -
Add your custom message as new line:
GLOBAL_RCPT_BL {
type = "rcpt";
map = "${LOCAL_CONFDIR}/custom/global_rcpt_blacklist.map";
regexp = true;
prefilter = true;
action = "reject";
message = "Sending mail to this recipient is prohibited by postmaster@your.domain";
}
- Save the file and restart Rspamd:
docker compose restart rspamd-mailcow.
Discard instead of reject¶
If you want to silently drop a message, create or edit the file data/conf/rspamd/override.d/worker-proxy.custom.inc and add the following content:
discard_on_reject = true;
Restart Rspamd:
docker compose restart rspamd-mailcow
Wipe all ratelimit keys¶
If you don't want to use the UI and instead wipe all keys in the Redis database, you can use redis-cli for that task:
docker compose exec redis-mailcow sh
# Unlink (available in Redis >=4.) will delete in the backgronud
redis-cli --scan --pattern RL* | xargs redis-cli unlink
Restart Rspamd:
docker compose restart rspamd-mailcow
Trigger a resend of quarantine notifications¶
Should be used for debugging only!
docker compose exec dovecot-mailcow bash
mysql -umailcow -p$DBPASS mailcow -e "update quarantine set notified = 0;"
redis-cli -h redis DEL Q_LAST_NOTIFIED
quarantine_notify.py
Increase history retention¶
By default Rspamd keeps 1000 elements in the history.
The history is stored compressed.
It is recommended not to use a disproportionate high value here, try something along 5000 or 10000 and see how your server handles it:
Edit data/conf/rspamd/local.d/history_redis.conf:
nrows = 1000; # change this value
Restart Rspamd afterwards: docker compose restart rspamd-mailcow