Filtering mails

We filter incoming mails with Rspamd which uses multiple filtering and statistical methods to generate a spam score, including (but not limited to) SPF, DMARC and DNS blacklists. Mails with a score greater than 10 get rejected. We are using Bayes filtering using the sqlite3 backend per server. To allow for some initial filtering we are retrieving example spam/ham databases provided by rspamd.com. We also autolearn ham and spam, what means that every mail with a negative score is auto-learned as ham, while every mail with a score higher than the rejection score is auto-learned as spam, given that the Bayes filter hasn’t already identified it as ham or spam.

Tip

We are working on a feature to let all users train the filter and to recategorize spam and ham by using appropriate folders.

Configure spam folder

Use uberspace mail spamfolder to configure the spam folder for all mailboxes in your account. Mails with a spam score greater than 5 will get sorted into the Spam folder in the according mailbox.

[eliza@dolittle ~]$ uberspace mail spamfolder status
The spam folder is enabled.
[eliza@dolittle ~]$ uberspace mail spamfolder disable
The spam folder is now disabled.
[eliza@dolittle ~]$ uberspace mail spamfolder enable
The spam folder is now enabled.

Background

We implement the spam folder by manipulating your ~/.qmail-default. Enabling spam folders effectively means that a maildrop filter named ~/.spamfolder is created which just includes the global template /opt/uberspace/etc/spamfolder.template. That global template basically resembles what vdeliver does - retrieving the target Maildir and optional mail forward targets. Disabling spam folders effectively means resetting ~/.qmail-default to call vdeliver instead of maildrop.

Warning

Spam filtering and sorting does not work with the system mailbox. Create user mailboxes instead!