"at" command and mail

[Robert Bonomi]

> Date: Sat, 03 Sep 2011 15:42:20 -0600
> To: questions at freebsd.org
> From: Brett Glass <brett at lariat.net>
> Subject: Re: "at" command and mail
>
> At 02:35 PM 9/3/2011, Robert Bonomi wrote:
>  
> >Is 'atrun' actually sending the mails or is 'cron' doing it?  'atrun' is
> >invoked by 'cron', from a specification in the system crontab file.
>
> /usr/src/libexec/atrun/atrun.c shows an invocation of sendmail(8) directly
> from atrun(8).

Hard to question that.  I like somebody with a truely authoritative answer!

This also provides an 'obvious' solution to the OP's problem.

Make a 'sendmail' substitute -- a simple script, say,  that does what you 
want.  the command output will be on stdin, and the 'user' will be a 
parameter to the script.