"Dave" == Dave Crocker <dhc@xxxxxxxxxxxx> writes:
Dave> Because there is no such value as "envelope sender".
I use the term "envelope sender" to mean the MAIL FROM address. I regard this as common usage.
The purpose of fetchmail is to obtain mail by verious means (often POP or IMAP) that may not give direct access to the envelope, and to reinsert the mail into the SMTP stream.
It is typically used by people who have POP accounts but want to deliver their mail to an MTA on a local machine.
In order to do this it needs to determine a "sensible" value to use for the SMTP MAIL FROM when transfering the mail to the local MTA. As you'll see from the posted algorithm, it's first choice is to use the *actual* previous value of the MAIL FROM, as identified by the Return-Path header. If this isn't available, as a fallback it appears to use something very similar to the PRA algorithm, with a couple of extra cases at the end.
As I said before, this is a red herring. The only reason the fetchmail algorithm exists is because it has to operate in an environment where the value of MAIL FROM isn't available.
I don't see its relevent to MARID work.