msmtp is an SMTP client.
In the default mode, it transmits a mail to an SMTP server (for example at a free mail provider) which takes care of further delivery.
To use this program with your mail user agent (MUA), create a configuration file with your mail account(s) and tell your MUA to call msmtp instead of /usr/sbin/sendmail.
Features include:
-Sendmail compatible interface (command line options and exit codes).
-TLS/SSL support, including client certificates.
-Authentication methods PLAIN, LOGIN, CRAM-MD5, EXTERNAL, SCRAM-SHA-1, DIGEST-MD5, and NTLM.
-IDN support.
-PIPELINING support for increased transmission speed.
-DSN (Delivery Status Notification) support.
-RMQS (Remote Message Queue Starting) support (ETRN keyword).
-IPv6 support.
-LMTP support.
-Support for multiple accounts.
To get more information run
msmtp --version