You need a script. If you have FM Server you can set scripts to run as cron jobs would. With FM Pro, you would have to trigger the script, as far as I know.
You could set the script up in a loop that
Send batch of email
Pause/Resume [Specify Hour interval in seconds here]
Exit Loop if [check to see if all email has been sent]
This is just a general outline. There's a lot of detail missing that depends on the structure of your database and what exactly you need to do with it.
You'll also need to make sure you have things configured correctly so that filemaker can send out the email in the first place. I haven't had to do that, have noted some threads here where others have needed help setting this up.