Manage spams with dovecot
You might want to help the anti-spam to learn if it missed spams or got wrong for some messages.
If you use dovecot and a mail client with IMAP protocol, you can move spams in "Junk" folder so the anti-spam recognize them in the future. On the contrary, moving a mail from "Junk" to "INBOX" folder indicates it is legitimate.
No matter if you use rspamd or spammassassin, we will see both. 3 steps are necessary :
1. Install dovecot plugin.
2. Enable and configure the plugin.
3. Create scripts so the anti-spam can learn.
It is described in dovecot documentation (you should read 😉)
First, let's install dovecot pigeonhole plugin :
# pkg_add dovecot-pigeonhole
Add "imap_sieve" in plugins list to enable it at the end of "/etc/dovecot/local.conf" :
protocol imap {
mail_plugins = $mail_plugins imap_sieve
}
Then, still in dovecot's local.conf, configure sieve plugin si it run scrits according to where messages are moved..
plugin {
sieve_plugins = sieve_imapsieve sieve_extprograms
# When a message is moved in Junk folder; report as spam
imapsieve_mailbox1_name = Junk
imapsieve_mailbox1_causes = COPY
imapsieve_mailbox1_before = file:/usr/local/lib/dovecot/sieve/report-spam.sieve
# When a mail is removed from Junk folder : it is nor a spam
imapsieve_mailbox2_name = *
imapsieve_mailbox2_from = Junk
imapsieve_mailbox2_causes = COPY
imapsieve_mailbox2_before = file:/usr/local/lib/dovecot/sieve/report-ham.sieve
sieve_pipe_bin_dir = /usr/local/lib/dovecot/sieve
sieve_global_extensions = +vnd.dovecot.pipe +vnd.dovecot.execute
}
Now create two files in the directory "/usr/local/lib/dovecot/sieve/".
The first is "report-spam.sieve":
require ["vnd.dovecot.pipe", "copy", "imapsieve", "environment", "variables"];
if environment :matches "imap.user" "*" {
set "username" "${1}";
}
pipe :copy "learn-spam.sh" [ "${username}" ];
The second is "report-ham.sieve" :
require ["vnd.dovecot.pipe", "copy", "imapsieve", "environment", "variables"];
if environment :matches "imap.mailbox" "*" {
set "mailbox" "${1}";
}
if string "${mailbox}" "Trash" {
stop;
}
if environment :matches "imap.user" "*" {
set "username" "${1}";
}
pipe :copy "learn-ham.sh" [ "${username}" ];
Now reload dovecot and compile the above scripts :
# rcctl restart dovecot # sievec /usr/local/lib/dovecot/sieve/report-spam.sieve # sievec /usr/local/lib/dovecot/sieve/report-ham.sieve
As you may have notices, the above files call "learn-spam.sh" and "learn-ham.sh". Thoses scripts will be different wether you use rspamd or spammassassin since they don't learn spams/hams with the same command. Read the next part 😉.
Learning scripts.
Scripts below are stored in "/usr/local/lib/dovecot/sieve".
For spamassassin
#!/bin/sh
#learn-spam.sh
/usr/local/bin/spamc -u ${1} -L spam -C report
#!/bin/sh
# learn-ham.sh
/usr/loca/bin/spamc -u ${1} -L ham -C report
for rspamd
#!/bin/sh
#learn-spam.sh
exec /usr/local/bin/rspamc -d "${1}" learn_spam
#!/bin/sh
# learn-ham.sh
exec /usr/local/bin/rspamc -d "${1}" learn_ham
For both :
Scripts must be executables :
# chmod +x /usr/local/lib/dovecot/sieve/learn-*.sh
At last, reload dovecot:
# rcctl reload dovecot
Here you go, now your anti-spam will learn when you'll move messages in approriate folders.