I’m not sure but I have the impression that ASCII mail notifications require /usr/sbin/sendmail while HTML mail notifications do not because that notification plugin uses the Python smtplib.
Have you tried HTML mails instead of ASCII?
I’m not sure but I have the impression that ASCII mail notifications require /usr/sbin/sendmail while HTML mail notifications do not because that notification plugin uses the Python smtplib.
Have you tried HTML mails instead of ASCII?