Mail sendmail

A blast from the past!

Sendmail is a popular open-source mail transfer agent (MTA) that was widely used in the past to send and receive email. It was first developed in the 1970s and was the de facto standard for email delivery on Unix-like systems.

Here's a brief overview of how sendmail works:

How Sendmail Works

  1. Mail Submission: When you send an email using a mail client (e.g., Microsoft Outlook, Mozilla Thunderbird), the email is submitted to the sendmail daemon (a process that runs in the background) on your local machine.
  2. Local Delivery: The sendmail daemon checks the email's recipient address and determines whether it's a local user or a remote recipient. If it's a local user, the email is delivered to the user's mailbox.
  3. Relay: If the recipient is not local, the sendmail daemon relays the email to a remote mail server, which is usually specified in the email's Received header.
  4. Routing: The remote mail server receives the email and routes it to the final destination, which may involve multiple hops through other mail servers.
  5. Delivery: The email is delivered to the recipient's mailbox on the remote server.

Sendmail Configuration

Sendmail is highly configurable, and its configuration files are typically stored in /etc/sendmail.cf (or /etc/mail/sendmail.cf on some systems). The configuration file specifies various settings, such as:

Sendmail Alternatives

While sendmail is still widely used, there are other popular MTA alternatives, such as:

Conclusion

Sendmail is a powerful and flexible MTA that has been widely used for many years. While it's still supported and maintained, it's not as widely used as it once was, and many modern systems have adopted alternative MTAs.