Spam handling

Incoming 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 blocklists.

You can train the filter by moving mails into the Spam folder in your mailbox, mails moved out of the Spam folder will be learned as ham (= good mails).

We also autolearn ham and spam, which 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 them).

Configure spamfolder

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

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

Note

Mails within the spam folder are auto-expunged after 30 days.

Tip

If you want to change the rejection score, please have a look at the examples in our description for Sieve.

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 username@uber.space. Create user mailboxes instead!

Outgoing Mails

SPF

The Sender Policy Framework (SPF) is a system that allows mailservers to check if another mail server is allowed to send mails for a specific domain. To specify which servers are allowed to send mails for your domain, you can set a TXT DNS record. Adding Uberspace hosts to the list of allowed servers for your domain will increase your chances of passing spam filters. This instructs other mail servers to accept mails from your domain if they originate from our hosts and to deliver any mails that claim to be from your domain but originate from a different server to the spam folder.

DKIM

DomainKeys Identified Mail (DKIM) allows the receiver to check that an email claimed to have come from a specific domain was indeed authorized by the owner of that domain. It achieves this by affixing a digital signature, linked to a domain name, to each outgoing email message.

We generate a DKIM key for every user, you can get yours with uberspace records list:

[isabell@stardust ~]$ uberspace records list
$ORIGIN isabell.example
@                    IN   MX 0 stardust.uberspace.de.
@                    IN  TXT "v=spf1 include:spf.uberspace.de ~all"
uberspace._domainkey IN  TXT "v=DKIM1;t=s;n=core;p=MIICIj...=="

[isabell@stardust ~]$