human
mailto: example with subject line
gpt
Here's how the mailto: URL should be composed:

    mailto:example@example.com?subject=Hello%20World

Replace "example@example.com" with your intended email address and replace the subject text with your desired subject, but remember to put in "%20" in place of any spaces.  Some browsers may be able to automatically replace the spaces with "%20" while some may not.
human
Thank you!
gpt
You're welcome! If you have any more questions, feel free to ask.