Re: [ietf-smtp] loop homework, not an experiment, draft-crocker-email-de

> > If you want a header that records the envelope address, Exim calls that 
> > Envelope-To:
> > I don't see any benefit to conflating that with a loop breaking token.
> Why use one field that is sufficient when we can pretend two are needed?
This is the sort of thing we can describe in the survey of existing usage, 
for the benefit of people less familiar with the way mail systems work.
When mail systems do internal forwards using things like .forward or 
/etc/alias, each forward adds a Delivered-To, which breaks a->b->c->a 
loops.  Since there's no SMTP involved, there's usually no Received and 
never an Envelope-To.  Also, as Sam, Viktor, and I have explained, the 
internal forwards are not necessarily to or from anything that has an 
externally valid envelope address.
Regards,
John Levine, johnl(_at_)taugh(_dot_)com, Taughannock Networks, Trumansburg NY
Please consider the environment before reading this e-mail. https://jl.ly

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