Fresh VPS: Why is mail not being sent?

Question

send mail

I took a fresh VPS on ubuntu
No mail is sent from the command line
echo "This is a test." | mail -s Testing [email protected]
How to check why?
What can be installed with minimal settings, what would work, without any mysql settings, etc.
The task is simply to receive letters from the command line.

Answer 1

So receive or send?
If sent, then - https://debian.pro/?s=exim4