RFE: Cache DMARC lookups
In https://www.mail-archive.com/mailman-users@python.org/msg71442.html, a user describes a failure to lookup a DMARC policy, leading to distributing a post from a p=reject host.
I suggest (1) keeping a cache of DMARC results for hosts for fallback when lookup fails, which would allow (2) quarantining posts if both the DNS lookup and the cache lookup fail. This could also be attached to the email database.