mail-server: add `dmarcReporting.excludeDomains`
The option exclude_domains for dmarc reporting in rspamd[1] allows
to configure a list of domains and/or eSLDs (external effective second level
domain) to be excluded from dmarc reports.
Helpful because e.g. dmarc reports to hotmail.com always fail for me with the following undeliverable notification:
The recipient's mailbox is full and can't accept messages now.