Mailto: links on form submit are not reliable for several reasons.
- Most web mail users do not have Outlook or similar e-mail clients installed on their system. When they click your submit button, nothing will happen.
- Mailto: links do not hide your e-mail address from harvesters and spam bots.
- Your form is not secure from spam bots and hackers.
AFAIK, Muse does not support server-side scripting. But that shouldn't preclude you from using a contact form with a separate form-to-email processing script. You point your HTML form to the script using the action attribute.
Which script depends on your server. Ask your hosting provider if they have scripts you can use. If they don't, find out which server-side languages your hosting plan supports -- php, asp.net, coldfusion, perl, etc...
This will narrow your search form appropriate scripts you can use.
Thanks for your answer! I am going to use PHPMailer, is that fine?
If your server supports PHP scripts, it should be OK to use that one.