Msmtp

Msmtp is an SMTP client with a sendmail compatible interface. It can be used with Mutt and other mail user agents. 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, GSSAPI, SCRAM-SHA-1, DIGEST-MD5, and NTLM, PIPELINING support for increased transmission speed, DSN (Delivery Status Notification) support, RMQS (Remote Message Queue Starting) support (ETRN keyword), IPv6 support, LMTP support, and support for multiple accounts.