Sidemail - The simplest way to send transactional emails. Sidemail makes sending transactional emails trivial, it's perfect for side projects, MVPs or the next big thing.
AuthSMTP - AuthSMTP is the outgoing SMTP email service for e-commerce websites, mailing lists or email applications.
Mailivery - Reach the Inbox, not the spam folder.
BriteVerify - Email Validation & Email Verification reduces bounce rates up to 98%. Rapidly verifying email addresses has never been easier, just drag drop and deliver!
Postal - Open source mail delivery platform, alternative to Mailgun or Sendgrid
CritSend - CritSend is a SMTP relay for developers.