Courier-MTA VS CMail

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.