Google Apps (now called "G Suite"). $5/month, stable, "just works," and via Google Docs/Drive you have a CRM solution. Alternatively Office 365 Business Premiu

Google Apps (now called "G Suite"). $5/month, stable, "just works," and via Google Docs/Drive you have a CRM solution. Alternatively Office 365 Business Premium. $12.50/month (12 month minimum commitment). Only reason you'd consider this is that it includes Email, Office Desktop Suite (Outlook, Word, Excel, etc), and CRM. Essentially you'd merge a couple of bills into one bill. Both are alright support, good uptime, great vendor support, good scaling, and migration strategies (in and out). PS - Yes, this is the "boring" and "obvious" answer but sometimes things are "boring" and "obvious" for a good reason.