zed email notifications don't work

[lnicola]

System information

Type	Version/Name
Distribution Name	Arch Linux
Distribution Version	N/A
Linux Kernel	5.12.10-arch1-1
Architecture	x86_64
ZFS Version	2.1.99-314_gff3175040
SPL Version	2.1.99-314_gff3175040

Describe the problem you're observing

Email notifications don't work.

Describe how to reproduce the problem

Configure email notifications, set them to verbose, leave ZED_EMAIL_OPTS unset, then start a scrub.

Include any warning/errors/backtraces from the system logs

[pid 3221429] execve("/usr/bin/mail", ["mail", "-s", "'ZFS", "scrub_finish", "event", "for", "tank", "on", "nas.home'", "me@domain"], 0x55a8699eb2a0 /* 28 vars */) = 0

It looks like the quotes in -s '@SUBJECT@' @ADDRESS@ don't prevent splitting the string into multiple arguments. Same with ZED_EMAIL_OPTS="-s 'scrub result' @ADDRESS@".

CC #6246