/etc/mailname and cron

[tony B]

i just got a note from my isp, and the monthly cron job output from my
machine got mailed to their root account.  i think they don't like that.
i must have fubar'd some domain stuff during install
because /etc/mailname had their domain rather than localhost.localdomain
in it.  I changed the file and tested it by running:

sudo run-parts --report /etc/cron.monthly

It seemed to run ok, but no mail showed up.  If, as I suspect, my isp
got another copy, there must be something else I need to do.  Or perhaps
I misunderstand the function of this file.

I'm sure the isp guys have plenty to do without fielding spurious mail
to their root account.  Can anyone suggest what i might do next?

Thanks,
tony