Simple Mail Transfer Protocol

Simple Mail Transfer Protocol (SMTP) is an Internet standard for electronic mail (email) transmission. First defined by RFC 821 in 1982, it was last updated in 2008 with the Extended SMTP additions by RFC 5321—which is the protocol in widespread use today.

SMTP by default uses TCP port 25. The protocol for mail submission is the same, but uses port 587. SMTP connections secured by SSL, known as SMTPS, default to port 465 (nonstandard, but sometimes used for legacy reasons).

Although electronic mail servers and other mail transfer agents use SMTP to send and receive mail messages, user-level client mail applications typically use SMTP only for sending messages to a mail server for relaying. For receiving messages, client applications usually use either POP3 or IMAP.

Although proprietary systems (such as Microsoft Exchange and IBM Notes) and webmail systems (such as Outlook.com, Gmail and Yahoo! Mail) use their own non-standard protocols to access mail box accounts on their own mail servers, all use SMTP when sending or receiving email from outside their own systems.

SMTP (company)

SMTP, Inc. is a provider of transactional and email marketing email delivery services based in Cambridge, Massachusetts, United States.

Services

SMTP, Inc. is a cloud service provider that specializes in sending outgoing email for large volume senders. In this regard SMTP is more akin to a technology service provider such as Amazon.com or Rackspace than email marketing company like Constant Contact. SMTP also offers related services such as tracking and reporting, reputation management, statistical analysis and expert support.

SMTP also provides tools for checking a domain’s DKIM records in DNS as well as for checking forward-confirmed reverse DNS (FCdDNS) for an IP.

The SMTP email delivery service requires that the emails are generated locally from a locally-kept emailing list.

SMTP runs its own redundant data center in the Hurricane Electric and XO Communications facility in Fremont, California.

History

The company was founded as EMUmail Inc. in 1998 by Matt Mankins. Three years later Mankins sold EMUmail to the software development company AccuRev. About a year later, former AccuRev CEO and EMUmail board member Semyon Dukach bought EMUmail.