gomail allows you to send email from the command line. It supports TLS, and SMTP authentication, but has no external dependencies.

It has been tested with GMail's SMTP servers, and may well work with others. Please let us know if it works for you.

Because gomail has no external dependencies, you may be able to grab a binary for your os/arch and go.

If you have the Go language tools installed, it's as easy as:

go install github.com/laslowh/gomail

If you don't have the Go language tools installed, check it out.