The kioslave mailto is responsible for launching the mail composer of your choice when you open a URL in the mailto scheme (RFC6068).
The syntax of a mailto URL follows the following pattern:
where recipients form a list of restricted SMTP address specifications, and the query part may contain one or more of the following parameters:
Specifies additional recipients.
Specifies additional recipients of carbon copies.
Specifies additional recipients of blind carbon copies. These recipients will receive the message, but all other recipients will not know about that.
Specifies the text of the message. This text should not be long, as there may be hard limits on how long an URL may be.
Specifies the subject of the message.
Choose the application to handle mailto locators in System Settings module → in the category Personalization.