When I try to send out email containing pics, from my dell opiplex755,using windows xp, I get this message, it also goes on to say (please verify that you have entered the server name correctly Account "PoP3",server.'PoP3',Protocol

SENDING requires the SMTP address rather than POP (delivery).
Occasionally MAIL is used in place of both POP and SMTP.
Check with your mail provider.

Would you please explain the difference between the two in plain talk , and how to fix it again thanks for your reply

POP - Post Office Protocol - INcoming mail
SMTP - Simple Mail Transfer Protocol - OUTgoing mail