Ricardo Wurmus writes: > I see that mumi fails to render https://issues.guix.gnu.org/issue/37444. This is due to an invalid charset in the Content-Type header of message 107 (debbugs numbering). In the event of such invalid Content-Type headers, RFC2045 recommends assuming the default Content-Type header. I have now implemented this recommendation in guile-email. See commit https://git.systemreboot.net/guile-email/commit/?id=6159257c9da3664c516a26fad1ee942068fbbdd2 Could you try again with this latest fix and let me know if it works?