GMass - GMass allows you to easily schedule emails, send out mass emails and mail merge campaigns and more with Gmail! Click here to learn about more features!
Recurrr - Send recurring emails
Quokka (formerly Kryptowire) - The gold standard in SAST, MAST, IAST, and more!
Right Inbox - Schedule Emails in Gmail To Be Sent Later
HubSpot Free Email Marketing - Powerful drag and drop email marketing in the HubSpot CRM
SendRecurring - SendRecurring allows you to setup, send, and maintain scheduled email reminders.