sendmail

Send email from the command line.

Send a message with the content of message.txt to the mail folder of local user user_name:

sendmail {{user_name}} < {{message.txt}}

Send an email from you@yourdomain.com (assuming the mail server is configured for this) to test@gmail.com containing the message in message.txt:

sendmail -f {{you@yourdomain.com}} {{test@gmail.com}} < {{message.txt}}

Send an email from you@yourdomain.com (assuming the mail server is configured for this) to test@gmail.com containing the file file.zip:

sendmail -f {{you@yourdomain.com}} {{test@gmail.com}} < {{file.zip}}