msmtp is an SMTP client.
msmtp runs on a wide variety of platforms. It needs little more than an ANSI C compiler and Berkeley-style sockets.
Supported platforms include: GNU/Linux (glibc, uclibc or dietlibc), Free/Net/OpenBSD, Solaris, AIX, HP-UX, MacOS X, OpenDarwin, Cygwin on Win32, Windows 9x/ME/NT/2000/XP/2003, MS-DOS/FreeDOS+DJGPP+Watt32.
Sendmail compatible interface (command line options and exit codes).
Authentication methods PLAIN, LOGIN, CRAM-MD5, DIGEST-MD5, GSSAPI, and NTLM.
TLS/SSL both in SMTP-over-SSL mode and in STARTTLS mode. Full certificate trust checks can be performed. A client certificate can be sent.
Fast SMTP implementation using command pipelining.
Support for Internationalized Domain Names (IDN).
DSN (Delivery Status Notification) support.
RMQS (Remote Message Queue Starting) support (ETRN keyword).
sendmail.exe is a simple windows console application that emulates sendmail's "-t" option to deliver emails piped via stdin.
if you require TLS/SSL support, download sendmail-SSL.zip