To open their email platform with the email address and subject already pre-populated, the user should right-clicking on the email link. This option allows the user to copy the email address or see other options that might help with composing the email in their email client.
However, if the link is formatted correctly as a "mailto" link in the document, simply clicking on it (not holding any keys) should also open the email client with the email address and subject populated. The specific action can vary based on the user's settings and the email client they use.
For the specific options provided, right-clicking is usually the most reliable method to access specific functionalities or settings related to links.