[danpalmer]

Intercom already mentioned may be a bit big.

There’s also Vero and Iterable that I’ve used. Iterable was pretty terrible and we ended up replacing it with in house tooling, Vero has been really great and we’re investing more in our Vero setup.

[tomnipotent]

While Intercom offers a great messaging feature set, it's far from being a complete CRM. Many other potential targets with more complete offerings.