OK, let's start over - what is the program you are trying to use? Windows Mail, Thunderbird, Eudora, Outlook, ....
Has it ever worked with sending mail before this?
have you ever sent pictures before this?
Are you trying to send the picture from a web page directly, using your *browser*?
For reference: POP3 (Post Office Protocol v3) is a protocol - like TCP/IP. Internet explorer *uses* TCP/IP but you don't go to TCP/IP when you visit a web page - you visit a server, like the one here called Vistax64.com. The same holds true for email - for most setups, you don't just send mail via something named POP3 - that is the protocol - more than likely your need to send it via something like pop.cox.net.
Also, realize that the POP3 protocol is for *receiving* mail - not sending mail. most often mail that is leaving your computer makes use of another protocol called SMTP (Simple Mail Transfer Protocol).
Finally, if you are trying to send this to someone using your browser, we need to know the browser. If you copied the picture on your HD and are trying to send it there, we need to know the program you are using. That is why I asked all those questions before - we *really* need those answered before we can say "Do this" or "Change that."