Is it the same attaching a 2MB file to an email or pasting the content of the file (the same 2MB file) and sending over the internet as an email;
What will be the bandwidth requirement to send both the files? (is it less if you paste the content than attaching it)
You would probably save a few bytes be copy/pasting the content as the subject; something like 30 bytes. But you are better off sending it as an attachment because it saves the receiver from having to copy/paste the contents (2 MB is huge) into a file and save it with the correct extension.