Send mail via SMTP server from command line

mailx -v -s "SMTP Test" -S smtp=smtp://smtp.stack1.com -S from="bob.clarke@stack1.com" john.smith@gmail.com

If you want to do the same without needing to terminate manually with a . (dot) or CTRL-D.. do this ...

cat email.content | mailx -v -s "SMTP Test" -S smtp=smtp://smtp.stack1.com -S from="bob.clarke@stack1.com" john.smith@gmail.com