Check out example codes for "mailto subject". It will help you in understanding the concepts better.

Code Example 1

How to add a subject to a "mailto" anchor in HTML.
<a href="mailto:[email protected]?Subject=Hello%20World">Contact me</a>
<!--	       |Recipitant Email   |Subject=Insert your Subject Line -->

Code Example 2

<a href="mailto:[email protected]?subject=Testing out mailto!">First Example</a>

Code Example 3

<a href="mailto:[email protected]?subject=Testing out mailto!&body=This is only a test!">Second Example</a>

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