PHP Radio Button Secure When Emailing

I've been trying to figure out if radio buttons and checkboxes need to be stripped (cleaned?) when sending them via email.

I have a contact form that just emails the information. It doesn't touch a database. Do I need to protect the radio buttons and checkboxes when emailing? Is it possible?

I haven't found anything on google regarding securing these when emailing them. I keep coming across a few answers that say that should definitely be protected when sending to a database. The same is found here, or questions regarding how to grab values or create one dynamically. So, I'm at a loss.

Do I secure radio buttons and checkboxes when emailing? Is it possible? Necessary? Here's what my code looks like, partially:

    $firstName = strip_tags($_POST['firstName']);
    $lastName = strip_tags($_POST['lastName']);
    $email = strip_tags($_POST['emailAddress']);
    $telNum = strip_tags($_POST['phoneNumber']);
    $colors= $_POST['eColors'];
    $additionalComments = strip_tags($_POST['additionalComments']);
    $spamField = strip_tags($_POST['sField']);


    <form id="contact-form" action="" method="post">

    <div>
            <input type="text" id="nameFirst" name="firstName" /> 
            <label for="nameFirst" class="nameIcon">
                <span>First Name</span>
            </label>
            <span class="hint">
                <p>Input hint goes here</p>
            </span>
        </div>

        <div>
            <input type="text" id="nameLast" name="lastName" />
            <label for="nameLast" class="nameIcon">
                <span>Last Name</span>
            </label>
            <span class="hint">
                <p>Input hint goes here</p>
            </span>
        </div>

        <div>
            <input type="email" id="eAddy" name="emailAddress" />
            <label for="eAddy" class="emailIcon">
                <span>Contact Email</span>
            </label>
            <span class="hint">
                <p>Input hint goes here</p>
            </span>
        </div>

        <div>
            <input type="tel" id="telNum" name="phoneNumber" />
            <label for="telNum" class="contactIcon">
                <span>Contact Number</span>
            </label>
            <span class="hint">
                <p>Input hint goes here</p>
            </span>
        </div>

        <div>
            <input type="checkbox" id="cbEColors" name="eColors" class="cbSwitch" />
            <label for="cbEColors">Do you expect more color?</label>
        </div>

        <div>
            <textarea id="addComments" name="additionalComments"></textarea>
            <label for="addComments" class="messageIcon">
                <span>Additional Comments</span>
            </label>
            <span class="hint">
                <p>Input hint goes here</p>
            </span>
        </div>

        <input type="text" id="sField" class="col" name="sField" />

        <button id="submit" name="submit" type="submit" value="Submit">Submit</button>

    </form>