s-nail fails with "Unable to (dot) lock mailbox, aborting operation: Permission denied"

[Rick Thomas <rbthomas@pobox.com>]

With recent Stretch installations the “mail” (or “mailx”) command is satisfied by the s-nail package.
As it comes fresh out of the box, s-nail has a problem with dotlock files.  For example:

> rbthomas@half:~$ mail
> Creating dotlock for "/var/mail/rbthomas" .....
> Unable to (dot) lock mailbox, aborting operation: Permission denied
> Creating dotlock for "/var/mail/rbthomas" .....
> Unable to (dot) lock mailbox, aborting operation: Permission denied
> rbthomas@half:~$ 

I don’t know if this is deliberate, or even whether this is the right fix, but the error can be made to go away by doing:

> sudo chown root:mail /usr/lib/s-nail/s-nail-privsep
> sudo chmod g+s /usr/lib/s-nail/s-nail-privsep

If the consensus is that it’s a bug, not a feature, I’ll submit a bug report.  I guess s-nail is the appropriate package?

Enjoy!
Rick