The short answer: it depends. You can send quite a few, I'm not sure if I ever exceeded the "limit of 500 per day" but I got close. If you do that these days there's a 99% chance you'll be banned though. You could get lucky and send hundreds of messages per day on a new account, but don't push it. Like I kind of mentioned before, newer accounts are more likely to be flagged. Just one example - Recently all my newer accounts got warnings that the age couldn't be set to 99 or 100, but my older ones were fine. There's not really a straightforward answer for this one