> The problem is when it comes to a service like yours, if it really is that hard to bulk mail, then the > guys using your service aren't the guys getting a 1 i

> The problem is when it comes to a service like yours, if it really is that hard to bulk mail, then the > guys using your service aren't the guys getting a 1 in 125m response rate. So for old school spammers even if they got lucky and got 1% click rate, they'd 1K clicks in their best day in our service. So I'm mostly considering them as people looking for potential holes in the service. The people coming with stolen credit cards who want to steal more are the biggest threat as they are most harmful - they hunt for our ips and domain reputation, so they take time and try pretty hard to break through our filters. > This too, but don't forget about simply cracking passwords for the accounts. Simple math. Take the top > 100 most used passwords, assume your users are just as naive as most the internet, and you have x% > users you can assume will be compromised at some point in the future. Yep, and we watch every account in the system for changes in behavior, but that's happened only once or twice in the last 2 months - so it's not a biggest problem right now.