What are some alternatives?
When comparing Email Studio for Gmail and SendLater, you can also consider the following products
If No Reply - Simple email automation that works for Gmail
Meekan - Connecting the world's calendars
Boomerang for iPhone - Email app + voice assistant from inventors of email snooze
Right Inbox - Schedule Emails in Gmail To Be Sent Later
Tettra - Tettra is a company wiki that helps teams manage and share organizational knowledge.
EmailPlayground - EmailPlayground provides solution to schedule and send emails with ease.