I know this question is probably very simplistic to most people. I have been in the real estate game for a number of years and never compiled a system for collecting potential buyers and a way to send them out emails at the appropriate time.  Most of my contracts I have closed on personally and I have primarily marketed for myself to the most part.  There has been some deals that came at a time where I already had projects going and it would have been best for me to have simply shared that deal with other buyers.

On a few occasions I have let a couple of wholesaler acquaintances help me find an adequate placement for a deal.  
What system and/or service are others using to collect, organize and send multiple emails at the appropriate time?