>> From: ludo@gnu.org (Ludovic Courtès)

On the other hand, I just realized that this is a non-standard Emacs
message mode parens style address described at
https://www.gnu.org/software/emacs/manual/html_node/emacs/Mail-Headers.html
. guile-email aims to support these non-standard addresses. So, I think
we can relax the requirement that email headers be strictly ASCII. I'll
push a fix and let you know.

Thanks,
Arun.