The CommuniGate Pro SMTP module implements E-mail message transfer using the SMTP and ESMTP Internet protocols via TCP/IP networks.
The Simple Mail Transfer Protocol allows computers to transfer messages using network connections. A computer that has a message to send connects to the recipient's computer and establishes a network link. Then it sends one or several messages and closes the network connection.
Mailer applications use the SMTP protocol to submit messages to the mail servers, and mail servers then forward the submitted messages to the recipients. All mailers have a setting called SMTP Host Address that specifies the network address of the mail server computer. Mailer applications open TCP connections to that address when they have a message to submit.
The CommuniGate Pro SMTP module supports special "secure ports" and the STARTTLS SMTP extension, and it can receive and send mail via secure (encrypted) connections.
The CommuniGate Pro SMTP module supports the AUTH extension and it allows remote users to authenticate themselves before submitting messages.
The CommuniGate Pro SMTP module also implements a protocol variation called LMTP (Local Mail Transfer Protocol).