I tried and failed at making a CRM.<p>The problem with developing and marketing CRMs is:<p>1. Very crowded space<p>2. You need to attract a lot of customers because revenue/customer for SaaS apps like CRMs are low: <a href="https://highrisehq.com/signup" rel="nofollow">https://highrisehq.com/signup</a> for example. When most of your customers will be on the free plan or paying you just $30-$40/month you'll need to attract 1000s in a very crowded space with plenty of low cost options around.<p>3. You can't tightly integrate email without going to a lot of trouble or resorting to a hack b/c Gmail and other services don't allow you to integrate their special sauce into your application. And IMAP isn't a viable option because of the low revenue/customer (IMAP is heavy and will cost you in bandwidth and storage).<p>4. Mission critical. If your CRM goes down even for a few minutes and you have 1000s of customers you're going to get a lot of angry phone calls. Not to mention a whole host of other issues that can go wrong like data loss, security breaches. Don't forget this is sensitive business data you'll be acting as a gatekeeper for. If something fails it'll be your head.
If you have no idea where to start, but you'd like to start a startup based off of the CRM, I'd start with<p><a href="http://www.paulgraham.com/articles.html" rel="nofollow">http://www.paulgraham.com/articles.html</a><p>and<p><a href="http://www.amazon.com/Startup-Owners-Manual-Step--ebook/dp/B009UMTMKS/ref=sr_1_1?s=books&ie=UTF8&qid=1380233613&sr=1-1&keywords=startup+owners+manual" rel="nofollow">http://www.amazon.com/Startup-Owners-Manual-Step--ebook/dp/B...</a><p>and see if that knocks out any ideas. There are several possible ways, but with CRMs, it is difficult in my opinion because the ones willing to pay good money for a CRM are the ones already looking at Salesforce CRM, and the other giants.