Sendmail

What is Sendmail?

Sendmail is a Mail Transfer Agent (MTA) - the software responsible for routing and delivering email across a network or the internet using SMTP.

If you think of an email as a physical letter, Sendmail is the high-speed sorting facility and the postal truck combined. For decades, Sendmail was the de facto standard on UNIX-based systems, and it powered the vast majority of the internet's email traffic.

How does Sendmail fit into the email process?

Sendmail is the middleman in an email's journey. It does not write the email (that is the job of the mail client, such as Outlook or Gmail), and it does not always store it for the recipient. Instead:

1. MUA (Mail User Agent): You hit "send" in your email app.
2. MTA (Sendmail): Sendmail receives the message, looks at the destination address, and moves the mail toward the right destination.
3. MDA (Mail Delivery Agent): Once the mail arrives, a delivery agent places it into the recipient's inbox.

What are the drawbacks of Sendmail?

Sendmail has several notable drawbacks:

• Age: It was designed in the early 1980s, before modern security standards existed.
• Platform limitations: It is natively a UNIX/Linux application, with no official Windows version.
• Deliverability: On shared hosting, many sites use the same Sendmail instance, so one bad neighbor sending spam can get the shared IP address blacklisted, catching your legitimate email in the crossfire. Older setups may also lack easy support for SPF, DKIM, and DMARC, which modern providers such as Gmail and Outlook now expect.

Sendmail and MIDAS

As of MIDAS v4.42, our software supports sending email via Sendmail, SMTP, and "Cloud". Up until v4.41, Sendmail was the default out-of-the-box email transport for cloud-hosted customers; from v4.42 the default for cloud-hosted customers is the new "Cloud" sending option.