> I've attached a file which should reproduce the issue.

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

There is an encoding error in the email, specifically in the From header
above. Notice the è in Courtès. It should have been encoded as a
"MIME-encoded word" using Quoted-Printable encoding or some other
scheme. See https://en.wikipedia.org/wiki/MIME#Encoded-Word . Only ASCII
characters are allowed in email headers. utf-8 characters are not
allowed. guile-email sees this character whose encoding it does not
understand and crashes with a decoding error. I should probably make it
raise a more meaningful error.

Could you provide more context for your code snippet? How does your
program come by this email string? Ideally, you should handle emails
only as bytevectors (or binary ports), not as strings. An email can have
characters encoded using different schemes, whereas a string is
constrained to have all characters encoded using the same scheme.

Regards,
Arun.