What is Sendmail?
Sendmail is a Mail Transfer Agent (MTA). If you think of an email as a physical letter, Sendmail is the high-speed sorting facility and the postal truck combined. It is the software responsible for routing and delivering email across a network or the internet using the Simple Mail Transfer Protocol (SMTP).For decades, Sendmail was the "de facto" standard for Unix-based systems and essentially powered the vast majority of the internet's email traffic.
How it Fits into the Email Process
To understand Sendmail, it helps to see where it sits in the journey of an email. It doesn't "write" the email (that's the MUA, like Outlook or Gmail) and it doesn't always "store" the email for the user (that's the MDA). It is the middleman.- MUA (Mail User Agent): You hit "send" in your email app.
- MTA (Mail Transfer Agent - Sendmail): Sendmail receives the message, looks at the destination address, talks to other servers, and moves the mail to the right destination.
- MDA (Mail Delivery Agent): Once the mail arrives at the correct server, a delivery agent puts it into the recipient's inbox.
Drawbacks of Sendmail
Sendmail has several notcable drawbacks.- Age: Sendmail was designed in the early 1980s before modern security standards existed.
- Platform limitations: Sendmail is natively a Unix/Linux application. There is no official Windows version of the Sendmail server.
- Performance: Sendmail can be slower under high server load.
- Deliverability & Spam Issues: Sendmail itself isn't "spammy," but its default behavior and the environments where it is often used (like shared hosting) create a perfect storm for low deliverability:
- IP Reputation: On a shared server, hundreds of websites use the same Sendmail instance. If one neighbor sends a spam blast, the server’s IP address gets blacklisted. Because Sendmail is the "messenger," your legitimate emails get caught in the crossfire.
- Lack of Modern Defaults: Modern MTAs like Postfix are often pre-configured with stricter "sanity checks." Older Sendmail setups may lack built-in, easy-to-enable protections for SPF, DKIM, and DMARC, which are now mandatory for reaching Gmail or Outlook inboxes.
- The "Open Relay" Risk: If misconfigured (which is easy to do in Sendmail), it can become an "open relay," allowing anyone on the internet to send spam through your server. This will get your server blacklisted globally within hours.
Sendmail and MIDAS
As of MIDAS v4.42, our software supports sending of email via Sendmail, SMTP, and "Cloud" ("Cloud" is new from v4.42 and is for cloud-hosted customers).Up until MIDAS v4.41 "Sendmail" was the default 'out of the box' email transport configuration for cloud-hosted customers. It was removed for cloud-hosted customers in v4.42. Now, the default for cloud-hosted customers is the new "Cloud" sending option.