I've never used paypal's recurrent billing before because I've never accepted paypal from my customers until recently. If I setup a customer to be billed $15/month recurring and this customer's CC declines or his/her payment fails for whatever reason... does paypal's system send me an email and notify me that this customer's payment declined that month?

Or must I use paypal in conjunction with some form of billing software to accomplish this? I couldn't find the answer anywhere to this...

Thanks.

Yes i would say that you would get notice :)

we've had that plenty of times, they'll just tell you the subscription payment failed and it'll retry in a few days. but if it does fail the first time I'd recommend contacting the client to correct it.