Mail-tags for custom HTML fields

I added HTML form fields to a Contact Form 7 form, for certain reasons.

Now I would like to access the values of these fields using a mail-tag, just like a native CF7 form field, so I can send the value in an email when the form is submitted?

For example: Let’s say I create a select element like this:

<select name="options">
    <option value="option1">Option 1</option>
    <option value="option2">Option 2</option>
</select>

Now, I was hoping I could use a mail-tag called [options] to access the value of the field. However, simply using a mail-tag identical to the name attribute of the HTML element does work.

Is there a way to accomplish this? If so, how?