Description:

msmtp is a simple program that works as an "SMTP plugin" for Mutt and
probably other MUAs (mail user agents). It forwards mails to an SMTP
server (for example at a free mail provider) which does the delivery.
Features include:
- PLAIN, LOGIN, CRAM-MD5, GSSAPI, DIGEST-MD5 and NTLM authentications
- TLS encrypted connections
- Internationalized Domain Names (IDN) support
- IPv6 support
- robustness
- detailed error messages if something goes wrong (including the full
answer of the SMTP server)
- sendmail compatible exit codes (which most MUAs understand).

Simply tell your MUA to call msmtp instead of /usr/sbin/sendmail (with
Mutt that's just one additional line in the config file).