Are you asking which CRM system is best for email marketing? In my experience none of them are particularly good, but the ones that handle the process better are the ones like Sage CRM that will integrate well with the likes of MailChimp. CRM is not a great emarketing tool to manage emarketing. MailChimp (and others) are dedicated products that are good at it. What you need is a CRM system that has good integration with an emarketing platform like MailChimp. CRM has inbuilt integration with MailChimp.

Start by finding an emarketing system/platform and then find which CRM systems integrate with it if your primary driver is emarketing. I'd then start by looking to get demos of the emarketing tool integrated with the CRM system.