Right Inbox - Schedule Emails in Gmail To Be Sent Later
Recurrr - Send recurring emails
SndLatr - SndLatr is a Gmail plugin that makes it easy to schedule emails to be sent automatically at a later time.
RGB Technologies - Email Scheduler - Email Scheduler provides an intuitive email scheduling solution, integrated within the existing Salesforce account.
SendRecurring - SendRecurring allows you to setup, send, and maintain scheduled email reminders.
Seventh Sense - Seventh Sense helps marketers and sales professionals reach the people that make them successful using artificial intelligence powered email.