Comment 3 for bug 1833331

If this works:

$ echo -e 'Subject: Test sendmail\n\nFoo' | /usr/sbin/sendmail <email address hidden>

but this does not:

$ echo Bar | mail -s 'Test mail' <email address hidden>

you should possibly address the issue to the maintainer of the mailutils package. I typically use the 'bsd-mailx' package as 'mail' provider and don't remember similar problems.

Alternatively you could disable (chmod -x) 10mail and add some /etc/smartmontools/run.d/11sendmail script, something like:

#!/bin/bash
/usr/sbin/sendmail $SMARTD_ADDRESS <<EOF
Subject: $SMARTD_SUBJECT
To: ${SMARTD_ADDRESS// /, }

$SMARTD_FULLMESSAGE
EOF

(Caution: not tested :-)