EmailPlayground - EmailPlayground provides solution to schedule and send emails with ease.
Email Studio for Gmail - Send personalized emails, schedule emails directly in Gmail
Right Inbox - Schedule Emails in Gmail To Be Sent Later
Seventh Sense - Seventh Sense helps marketers and sales professionals reach the people that make them successful using artificial intelligence powered email.
If No Reply - Simple email automation that works for Gmail
SndLatr - SndLatr is a Gmail plugin that makes it easy to schedule emails to be sent automatically at a later time.