Fixed zfs_notify_email for programs like sendmail

zfs_notify_email will now include an empty line separating the header
from the body of the email in case the subject is not provided via a
command line argument. This is necessary for programs like sendmail to
function correctly (everything up to the first empty line is interpreted
as header, which previously resulted in either missing message parts or
unsent emails)

Reviewed-by: Alexander Motin <[email protected]>
Signed-off-by: Felix Schmidt <[email protected]>
Closed #17238

Author: IIIPr0t0typ3III

cmd/zed/zed.d/zed-functions.sh

@@ -283,6 +283,11 @@ zed_notify_email()
         if [ "${ZED_EMAIL_OPTS%@SUBJECT@*}" = "${ZED_EMAIL_OPTS}" ] ; then
             # inject subject header
             printf "Subject: %s\n" "${subject}"
+            # The following empty line is needed to separate the header from the
+            # body of the message. Otherwise programs like sendmail will skip
+            # everything up to the first empty line (or wont send an email at
+            # all) and will still exit with exit code 0
+            printf "\n"
         fi
         # output message
         cat "${pathname}"