esmtp VS CMail

esmtp

esmtp is a user configurable relay-only Mail Transfer Agent (MTA) with a sendmail compatible syntax.

CMail

CMail is a free Windows command line mailer with advanced message formatting options.

Landing page //
2023-04-24

Image date //
2024-03-09

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.