How do you normally send and receive emails? Some people do it by using a proper email client (such as Outlook, Outlook Express, Windows Live Mail or Thunderbird). Other people do it by going to the web page of their email service.
When you use the 'scan to email' facility on a multi-function printer it launches your default email client (Outlook, etc, as above) with a fresh email already created (with the scanned image as an attachment to that email). you can then fill in the address and message before sending the mail.
However if you don't normally use that email client (because you use a web-based system instead) it won't have been configured with the relevant settings to enable it to access your mail provider's server. (So you won't be able to send the mail; you can't scan directly to a web-based service).
If the foregoing applies to you, you've got a choice of two ways of sending the scanned image:
1. You can configure your email client to work with your provider's server. (If you need instructions, please tell us which email client you've got and who provides your email service) ; or
2. You can scan the image to your PC in the normal way, then go to your web-based email service and attach the file to a new email.
If none of the above applies to you (because you've already got a properly configured email client) I apologise for wasting your time but I'd also suggest that it would be helpful to have an explanation of exactly how "it all seems to go wrong".
Chris