[Mailman-Developers] callbacks, Fixing DMARC problems with .invalid munge

[John R Levine]

> And, it’s not abusive if appropriate SPF checks are done first: obviously, you don’t do the callout if you get an SPF fail. A callout with an SPF pass isn’t abusive: if the domain sent me an email, then it should be able to handle a callout.

Let me just say that a lot of people at large ISPs disagree with you.

Considering that about 90% of mail is spam, and about 99% of spam has 
forged return addresses, in practice all of your callbacks are annoying 
people who had nothing to do with the spam.  If you're not getting 
complaints, it's because you're too small to be worth blocking.

Regards,
John Levine, johnl at taugh.com, Taughannock Networks, Trumansburg NY
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