Simplest way to send one-line mail out via command line using gmail?

Using Raspbian and Ubunntu 16.04 LTS so need a generic Linux solution. Requirement is simple: **I need a way to send one-line email messages from the command line.** I have set up a gmail account just for this particular Rpi3, with the address of rpi3abc@gmail.com - with no 2FA So now I need to be able to send one-line mail messages from anywhere (including cron) without user intervention. ----------------------- I also would like it to be able to send text files; basically, anything from stdin.