Basically there's a program to accomplish that, called "mail". The subject of the email can be specified with a -s and a list of address with -t. You can write the text on your own with the echo command:
echo "This will go into the body of the mail." | mail -s "Hello world" [email protected]
or get it from other files too:
mail -s "Hello world" [email protected] < /home/calvin/application.log
mail doesn't support the sending of attachments, but Mutt does:
echo "Sending an attachment." | mutt -a file.zip -s "attachment" [email protected]
Note that Mutt's much more complete than mail. You can find better explanation here
PS: thanks to @slhck who pointed out that my previous answer was awful. ;)