How to send an E-mail using the Linux command line (The Mutt Mail User Agent)

Yesterday I needed to send an e-mail with a file attached using the Linux command line. The solution was quite simple but I spent some very important minutes to find it. So there is it:

$ mutt -s "Mail's subject" -a file_to_attach.rar user@provider.com

I hope it could be useful to you one day.