# 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: . - 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}}" {{to_user@example.com}}` - Send an email that contains file content: `mail --subject="{{$HOSTNAME filename.txt}}" {{to_user@example.com}} < {{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}}" {{to_user@example.com}}`