mail

The command operates on the user's mailbox if no argument is given. To send an email the message body is built from stdin. More information: https://manned.org/mail.

• Send a typed email message. The command-line below continues after pressing Enter key. Input CC email-id (optional) press Enter key. Input message text (can be multiline). Press Ctrl-D key to complete the message text:
  mail --subject="{{subject line}}" {{[email protected]}}
• Send an email that contains file content:
  mail --subject="{{$HOSTNAME filename.txt}}" {{[email protected]}} < {{path/to/filename.txt}}
• Send a tar.gz file as an attachment:
  tar cvzf - {{path/to/directory1 path/to/directory2}} | uuencode {{data.tar.gz}} | mail --subject="{{subject_line}}" {{[email protected]}}