🚀 go-pugleaf

And address that is in a legal rfc822 format should obviously not
have myhost! added to it anywhere.

But those addresses are always "user@host...domain" where domain is one
of the legal top level domains, and most certainly "UUCP" isn't one
of them.

For addresses in "host!host!...!user" form, in the From_ or From: line,
you *must* add your own hostname, as that's all that makes the
address sensible.  That is, uucp hostnames are ambiguous, to
disambiguate them its essential to know the name of a host the
one in question is connected to, and to disambiguate that you need
to know the name of a host that one is connected to (other than the
first), and that has to continue all the way to your own host,
which is the only uucp name that you can be certain of by itself.

I know that lots of hosts don't do this, they're largely ones who
have mailers that have simply never heard of rfc822 or From: lines,
or ones who have been misguided by those who believe (rightly) that
domains are the only way this mess can survive, but who have gotten
ahead of themselves and assumed that anything can be made a domain
at random.

So, if you find a legal domain name, leave it alone.  If you don't
then the address should be kept in old style uucp format, and the
local host name should be added.  At least people who route their
mail through rational hosts will have it work.

Robert Elz