tumgreyspf 1.36-4.1 (amd64 binary) in ubuntu eoan

 Tumgreyspf can optionally greylist and/or use spfquery to check SPF records
 to determine if email should be accepted by your server. The default behavior
 is to let emails comming from server that are SPF approved without any sort
 of greylisting, while all others will be greylisted.
 .
 SPF is information published by the domain owner about what systems may
 legitimately send e-mail for the domain. Greylisting takes advantage of spam
 and viruses that do not follow the RFCs and retry deliveries on temporary
 failure. These checks can be used as part of a mail system and allow several
 orders of magnitude reduction in spam, lower system load, and few problems
 with legitimate mail getting blocked.
 .
 Tumgreyspf uses the file-system as its database, no additional database is
 required to use it, see /var/lib/tumgreyspf/data and it's clean-up cron
 script. Also take care that tumgreyspf will block emails from any domain with
 DNS configured with a buggy SPF record.