I use getresponse for my abandon cart sequences, welcome emails, sale announcements and regular broadcasts
Great affiliate tracking software and would definitely be a good integration for Subbly.
Make shipping cheaper and easier for me if I didn't have to export and then import into Pirateship manually for each customer.
Acuity or other scheduling app
Track and book service appointments. Or customer support calls/ business agendas for other people without services.
Affordable chat app, with real time monitoring, android, ios, pc and osx apps. A free plan for life and paid plans.