How to configure cron (and pam?) to allow mail from cron?

[Kynn Jones <kynnjo@gmail.com>]

I'm trying to set up a `cron` job that will send me mail for some outputs.

In my `crontab` I have the `MAILTO` variable set to my email address,
as well as the directives

* * * * * /bin/date >> /tmp/debug_cron
* * * * * /bin/date >&2

as a test (i.e. a proxy for the command I eventually want to run), but
I'm getting no mail from `cron`.  (I do get outptu in the
`/tmp/debug_cron` file.)

My `/var/log/auth.log` file shows many pairs of lines of the form:

Nov 14 17:25:01 myhost CRON[29571]: pam_unix(cron:session): session
opened for user myusername by (uid=0)
Nov 14 17:25:01 myhost CRON[29571]: pam_unix(cron:session): session
closed for user myusername

A new pair of such lines gets added every minute, which coincides with
the timing of my crontab commands.  Therefore, it may be that
`pam_unix` is blocking `cron`'s attempt to send me mail?  I don't know
how to pursue this possibility further.  (I have never done any
PAM-related configuration in my life, so whatever configuration I have
is either what "came out of the box" when I installed Debian, or was
carried out by some program without my intervention.)

(BTW, aside from what I've described above, nothing else in the logs
appears relevant to this question, even remotely so.)

How can I troubleshoot this problem further?

Thanks in advance for any advice!

kj

PS: FWIW, my `/etc/pam.conf` file contains only comments and
whitespace, and here are the contents (excluding comments and
whitespace) of other `pam` relevant config files:

    # /etc/pam.d/cron
    @include common-auth
    session    required     pam_loginuid.so
    session       required   pam_env.so
    session       required   pam_env.so envfile=/etc/default/locale
    @include common-account
    @include common-session-noninteractive
    session    required   pam_limits.so

    # /etc/pam.d/common-auth
    auth    [success=1 default=ignore]    pam_unix.so nullok_secure
    auth    requisite            pam_deny.so
    auth    required            pam_permit.so
    auth    optional            pam_cap.so

    # /etc/pam.d/common-account
    account    [success=1 new_authtok_reqd=done default=ignore]    pam_unix.so
    account    requisite            pam_deny.so
    account    required            pam_permit.so

    # /etc/pam.d/common-session-noninteractive
    session    [default=1]            pam_permit.so
    session    requisite            pam_deny.so
    session    required            pam_permit.so
    session    required    pam_unix.so