[kh99]

If you have vb4.2.0 you can do that with the Settings under Email Options. You need to set both "Use Mailqueue System" and "Use Cron Based Sending" to Yes, then you can set "Number of Emails to Send Per Batch" to control how many are sent per hour. Since the "Process E-Mail Queue" scheduled task is set to run every 10 minutes (6 times per hour), you'd set the Per Batch size to 1/6 of what you want to send out per hour.

But this isn't perfect - some emails like registration email verification (if you have that turned on) bypass the queue. Also the scheduled tasks depend on site traffic, so if you have a site that's not active for parts of the day, mail won't get sent out. (But any solution you come up with will have the same problem unless it somehow uses the operating system cron jobs).