Отправить электронное письмо, установив флажок html

Я пытаюсь своим клиентам выбрать, какие услуги они хотят получить по электронной почте. Я получил письмо, но сервисы пусты, мой php файл неверен. заранее спасибо

<h3>Tell us your inquiries</h3>

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<form id = "contact-form" action = "mailto:[email protected]" method = "post" onsubmit = "return checkform(this);">
<div class = "form-group">
<label for = "firstname">First Name <span class = "form-required" title = "This field is required.">*</span></label>
<input type = "text" name = "firstname" class = "form-control half" id = "firstname" required>
                                            </div>
                                            <div class = "form-group">
                                                <label for = "lastname">Last Name <span class = "form-required" title = "This field is required.">*</span></label>
                                                <input type = "text" name = "lastname" class = "form-control half" id = "lastname" required>
                                            </div>
                                            <div class = "form-group">
                                                <label for = "email">E-mail <span class = "form-required" title = "This field is required.">*</span></label>
                                                <input type = "email" name = "email" class = "form-control half" id = "email" required>
                                            </div>
                                            <div class = "form-group">
                                                <label for = "subject">Zip Code <span class = "form-required" title = "This field is required.">*</span></label>
                                                <input type = "text" name = "zipcode" class = "form-control half" id = "zipcode" required>
                                            </div>
                                            <div class = "form-group" >
                                                <label for = "email">Select Services</label>
                                            <div class = "row1">
                                                    <div class = "col1"><input id = "chk1" type = "checkbox"><label>As-Built</label></div>
                                                <div class = "col1"><input id = "chk2" type = "checkbox" onclick = "myFunction('New Construction Design','chk2')"/><label>New Construction Design</label></div>
                                                <div class = "col1"><input id = "chk3" type = "checkbox" onclick = "myFunction('Residential Remodels','chk3')"/><label>Residential Remodels</label></div>
                                                <div class = "col1"><input id = "chk4" type = "checkbox" onclick = "myFunction('Residential Additions','chk4')"/><label>Residential Additions</label></div>
                                                <div class = "col1"><input id = "chk5" type = "checkbox" onclick = "myFunction('3D Modeling and Renderings','chk5')"/><label>3D Modeling and Renderings</label></div>
                                                <div class = "col1"><input id = "chk6" type = "checkbox" onclick = "myFunction('Interior Design','chk6')"/><label>Interior Design</label></div>
                                                <div class = "col1"><input id = "chk7" type = "checkbox" onclick = "myFunction('Space Planning and Furniture Layouts','chk7')"/><label>Space Planning and Furniture Layouts</label></div>
                                                <div class = "col1"><input id = "chk8" type = "checkbox" onclick = "myFunction('Custom Furniture Design','chk8')"/><label>Custom Furniture Design</label></div>
                                                <div class = "col1"><input id = "chk9" type = "checkbox" onclick = "myFunction('Landscape Design','chk9')"/><label>Landscape Design</label></div>

                                            </div>
                                            </div>
                                                                                <div class = "form-group">
                                                <label for = "message">Message <span class = "form-required" title = "This field is required.">*</span></label>
                                                <textarea  name = "message" class = "form-control" rows = "4" id = "message" required></textarea>