CMail VS KumoMTA

CMail is a command line e-mail sending tool. It was originally developed to assist with testing mail server and content analysis software. As a result, CMail provides many more message formatting and SMTP session control options than similar software.

Features

• Flexible configuration via files or the command line and optional GUI provided by CMailGUI.
• TLS/SSL (including TLS 1.3) via STARTTLS or SMTPS (SSL-enabled version). Built-in, stunnel not required.
• Support for adding multipart/alternative HTML message bodies (UTF-8) and embedded images.
• SMTP authentication using CRAM-MD5, PLAIN, LOGIN, OAUTHBEARER and XOAUTH2.
• Unlimited attachments using base64, quoted printable or uuencoding.
• Wildcard attachment support to attach directory content.
• Unlimited To/Cc/Bcc recipients, with aliases and DSN options for each if desired.
• Message bodies using plain text, base64, or quoted printable encoding.
• IPv6 support.
• DKIM signing (RSA and Ed25519).
• Delivery Status Notification and Message Disposition Notification (Read receipt) support.
• Read message body from command line, stdin or file.
• Sending via SOCKS or HTTPS proxies.
• Works with GMail using App Passwords or user-supplied OAUTHBEARER/XOAUTH2 tokens.
• Written entirely in C - no need for .NET libraries, Java, or other prerequisites.
• No installation required. Download, extract, use.
• Free for private and commercial use.

The History of KumoMTA

KumoMTA is an open source Message Transfer Agent (MTA) designed to provide high performance outbound email functionality.

The KumoMTA project was founded by a group of email industry veterans with decades of experience building and managing high-performance On-Prem MTAs and is supported by a community of some of the largest senders in the world. While paying attention to the lessons of history, KumoMTA was designed from the ground up with new tech as opposed to modifying something that already existed. We specifically avoided making a modification of Postfix or Exim or some other existing MTA and instead wrote entirely new code in Rust.

What is a "Kumo"?

So how did we come up with the name KumoMTA? We set out to build a cloud deployable on-premises MTA that was flexible enough to install both on bare metal and in a public or private cloud. Kumo means cloud in Japanese, so "KumoMTA" is a Cloud MTA.

Why Open Source?

High volume commercial MTAs tend to have closed source code and steep license fees. Neither of these are particularly bad as long as the software is maintained and is flexible enough to modify. However, the kind of people who typically install very complex high-volume MTAs usually want to modify it or integrate it into other systems. Providing an open source option allows people to modify the code as needed, and contribute modifications easily to the community. The email community is full of very smart, creative people who now have an avenue to contribute to a wider community project.