Basically, doing a DNS lookup was too costly. Legitimate mail was being delayed. The current rule is one recipient who has an actual account.
Pass that test and the message will be scanned for other kinds of spam. Fail it and into the bit bucket.
Ok, so lets step back and ask: then why did you seem to have a problem with the idea of mail servers being responsible for filtering? I though your complaint about legit mails with a typo in the to address was a problem?
Pass that test and the message will be scanned for other kinds of spam. Fail it and into the bit bucket.
Sounds like a boiler plate template of how it should be done..