What are some alternatives?
When comparing Email Studio for Gmail and Calendly, you can also consider the following products
Meekan - Connecting the world's calendars
Acuity Scheduling - Automate your client bookings, cancellations, reminders & payments using the worlds friendliest online scheduling software.
If No Reply - Simple email automation that works for Gmail
Doodle - Make meetings happen. With Doodle, scheduling becomes quick and easy.
SendLater - Email scheduler for Mac Mail.
YouCanBook.me - YouCanBook.me is a cloud-based service which allows your customers to schedule appointments and make bookings.