1) Outgoing email initials 
Simple Mail Transfer Protocol
[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...
SMTP stands for Simple Mail Transport Protocol. It is the Internet email delivery format for transmitting email messages between servers.
Simple Mail Transfer Protocol - a method of passing email messages from one machine to another - the other popular mail protocol is POP
Simple Mail Transfer Protocol is a TCP protocol for mail transport running at the application layer. RFC 821, 822.
Simple Mail Transfer Protocol, details ...
The Simple Mail Transfer Protocol. 1. A specification given in RFC #821 for UNIX-style e-mail to be exchanged via several kinds of network transfer services, usually TCP. 
Simple Mail Transport Protocol
Simple Mail Transfer Protocol (SMTP) is the de facto standard for e-mail transmissions across the Internet.
Simple Mail Transfer Protocol: A protocol used to transfer email between servers.
Simple Mail Transfer Protocol: worldwide de facto electronic messaging standard. Limited to ASCII characters it facilitates mail between the Internet and other networks. 
Internet Simple Mail Transfer Protocol. A protocol which describes MTA and UA actions of an email system. SMTP uses MIME to encode complex data for transmission. SMTP and MIME are used to transfer MMS (the mobile Multimedia Message Service) between MMS MTAs.
Simple Mail Transfer Protocol
The main protocol used to send electronic mail from server to server on the Internet. SMTP is defined in RFC 821 and modified by many later RFC's.
SMTP or simple mail transfer protocol is the method used by most internet hosts to handle the transfer of email across the internet. It is a simple system in which all commands and text are transferred as text, so
Protocol to send email.
(NETWORK GLOSSARY) Simple mail transfer protocol. An Internet protocol providing electronic mail services.
(Simple Mail Transport Protocol) -- The Internet standard protocol for transferring electronic mail messages from one computer to another. SMTP specifies how two mail systems interface and the format of control messages they exchange to transfer mail.
Simple Mail Transfer Protocol. The Internet standard protocol for transferring electronic mail messages from one computer to another. 
When you're exchanging electronic mail on the Internet, SMTP is what keeps the process orderly. It's a protocol that regulates what goes on between the mail servers.
Simple Mail Transfer Protocol. The standard protocol for exchanging mail over TCP/IP networks.