send-mail is a basic yet efficient Linux software application written in C for SMTP email sending.
SMTP is an internationally accepted standard for transmitting email messages all over the internet. The protocol was officially defined in the RFC 821, which was later amended by RFC 1123, and currently, it is some variations of the ESMTP protocol that is used, which was defined in RFC 2821.
SMTP is a simple text-based protocol that involves one or more recipients being identified by the mail sender along with the message text and other encoded objects. After identification, the mail is transferred to a remote server, leveraging a string of queries and responses between the server and client.
An email client, also known as Mail User Agent (MUA), or a relaying server's MTA (Mail Transport Agents), can act as an SMTP client. The outgoing mail SMTP server can be accessed easily through the configuration of the email client. On the other hand, a relaying server determines the appropriate SMTP server to connect to, by lookup up the MX DNS record for each recipient's domain name of the email address. The relaying server can fallback on a simple A record if no MX DNS record is found.
The SMTP client establishes a TCP connection to the server's port 25 (potentially overridden by configuration). To test an SMTP server, you can use the telnet program, which is quite easy to use, and it does not require any additional installation.
SMTP, at its core, is a "push" protocol that does not support "pull" functionality to retrieve messages from remote SMTP servers. To access messages from remote servers, the email client needs to utilize POP3 or IMAP protocols. A triggering delivery can be initiated in SMTP using ETRN from another SMTP server.
In conclusion, Send-mail is an outstanding software for Linux users, which supports SMTP and helps users send emails with ease. SMTP is still the standard for email transmission, and to understand how to take advantage of it, you can leverage Send-mail as your go-to software.
Version 1.2.0: N/A