Has anyone else observed that a user authenticated via LDAP who runs a job with at(1) or cron never gets the e-mail with the job output? In fact the output seems to disappear. No one ever gets a copy and nothing appears in the way of error output in /var/log.
Mail from 'at' and 'cron' work fine for me, even for LDAP users.
Perhaps you have an MTA configuration error, is there any useful information in /var/log/maillog?