the pop3/send server has a bad address, or login/password is wrong. check with the isp website for email setup.
Are you able to send any emails from the phone?
How long have you been experiencing problems with sending emails with pictures?
Who is the email provider? It sounds as though you need to verify the outgoing server settings to ensure the emails are able to be sent from your phone.
Here is a link that will guide you through verifying/editing the settings.
If that fails, you may need to delete the email account completely and re-add it.