Crashes on email adresses with illegal characters

[philpagel]

When an email address contains invalid characters (i.e. on-ASCII) mailmerge crashes with a stack trace.
Expected behavior: some kind of error message instead of crash. Ideally, continuing to send the remaining emails.

Example: email: mü[email protected] which contains an umlaut that shouldn't be there.
Result: UnicodeEncodeError: 'ascii' codec can't encode character '\xfc' in position 10: ordinal not in range(128)

[awdeorio]

Thanks for your diligent reporting @philpagel ! This absolutely needs a unit test and a fix.

[philpagel]

After some more reading, it seems that non-ASCII characters are in fact allowed in email addresses if the smtp server announces support for the UTF8SMTP extension.
Sources:

• RFC5336 (obsolete)
• RFC6531 (proposed)