DKIM subdomain support

[FinnJanik]

Describe the bug
When I add a subdomain to froxlor, like some-name.domain.tld everything works fine, except the DKIM signature of the individual email messages. rsmapd tries to access /var/lib/rspamd/dkim/domain.tld.dkim.key, which ofcourse wasn't configured by froxlor, as the mail sending domain is some-name.domain.tld. After some research and debugging I found that when adding use_esld = false to the /etc/rspamd/local.d/dkim_signing.conf the DKIM signature is added to the message. Apparently rspamd only extracts the root domain part when using $domain as a variable.

System information

• Froxlor version: 2.2.6
• PHP sapi & version: php-fpm 8.3
• Web server: nginx
• DNS server: Bind
• POP/IMAP server: Dovecot
• SMTP server: postfix
• FTP server: proftpd
• OS/Version: Ubuntu 24.04.2 LTS

To Reproduce
Steps to reproduce the behavior:

1. Create a new domain in froxlor like some-domain.domain.tld
2. Enable the domain as EmailDomain and enable DomainKeys
3. Set the required DNS entries (spf, dmarc, dkim)
4. Create an inbox including account for the domain some-inbox@some-domain.domain.tld
5. Send an email from some-inbox@some-domain.domain.tld
6. Check that there is no DKIM signature attached to the email
7. Open the rspamd logfile and see, that it was tried to load the key file from domain.tld.dkim.key

Expected behavior
Also with non root domains DKIM signing should work as expected. use_esld = false should be added to the /etc/rspamd/local.d/dkim_signing.conf file in the froxlor configuration files.

Logfiles
2025-03-20 10:41:18 #149724(normal) <20CAB3>; lua; settings.lua:387: <608d5a05bf0990b55676c6707e51115e@some-domain.domain.tld> apply static settings frx_5806ae255305e63ec5e8a703d36114e0_from (id = 1198715664); from matched; priority medium 2025-03-20 10:41:18 #149724(normal) <20CAB3>; task; dkim_symbol_callback: skip DKIM checks for local networks and authorized users 2025-03-20 10:41:18 #149724(normal) <20CAB3>; lua; spf.lua:189: skip SPF checks for local networks and authorized users 2025-03-20 10:41:18 #149724(normal) <20CAB3>; lua; dmarc.lua:360: skip DMARC checks as either SPF or DKIM were not checked 2025-03-20 10:41:18 #149724(normal) <20CAB3>; task; dkim_module_load_key_format: cannot load dkim key /var/lib/rspamd/dkim/domain.tld.dkim.key: cannot stat key file: '/var/lib/rspamd/dkim/domain.tld.dkim.key' No such file or directory