Sending a mail from a linux shell script

Admitting you want to use some smtp server, you can do:

export SUBJECT=some_subject
export smtp=somehost:someport
export EMAIL=someaccount@somedomain
echo "some message" | mailx -s "$SUBJECT" "$EMAIL"

Change somehost, someport, and someaccount@somedomain to actual values that you would use. No encryption and no authentication is performed in this example.