Right Inbox - Schedule Emails in Gmail To Be Sent Later
AuthSMTP - AuthSMTP is the outgoing SMTP email service for e-commerce websites, mailing lists or email applications.
Recurrr - Send recurring emails
BriteVerify - Email Validation & Email Verification reduces bounce rates up to 98%. Rapidly verifying email addresses has never been easier, just drag drop and deliver!
FollowUpThen - The simplest way to schedule an email reminder
CritSend - CritSend is a SMTP relay for developers.