Truncated to something like fvv544+user@mydomain.com that would only be valid when sent with the from-adress new-sender@example.com (along with some clever magic to avoid email loops! :-)
I think maybe it was authored by ESR (Eric Raymond) in python - but Google only turns up various dkim schemes...
New senders would have their mail held back, and get a "please reply if you are human"-message - a reply (to the "magic" reply-to alias) would release the held mail and whitelist the sender.
base64encode(hmac("new-sender@example.com+valid-to+01012018", key))+user@mydomain.com
Truncated to something like fvv544+user@mydomain.com that would only be valid when sent with the from-adress new-sender@example.com (along with some clever magic to avoid email loops! :-)
I think maybe it was authored by ESR (Eric Raymond) in python - but Google only turns up various dkim schemes...
New senders would have their mail held back, and get a "please reply if you are human"-message - a reply (to the "magic" reply-to alias) would release the held mail and whitelist the sender.
A greylist variant of sorts.