Mail through Cron Execution does not work!

I’d say the first thing to check is whether or not the cron is actually running properly. Whenever I have issues like this, it’s usually with the cron run itself, not with the code it’s calling.

Remove all of the code inside your hooked function and replace it with a single line that sets an option–something named “my_cron_last_ran” or whatever–and set the option’s value to the current time. If the option doesn’t appear in your wp_options table, the cron hasn’t run properly.

The other troubleshooting thing I’d try is to remove everything but the mail stuff from your hooked function. If it runs and sends mail, then the issue could be that code BEFORE your mail stuff is erroring out and causing the whole thing to fail.