required

<input type="email"
                class="form-control"
                id="mail"
                name="mail"
                placeholder="Inserisci la tua e-mail"
                [(ngModel)]="model.mail"
                #mail="ngModel"
                required
                pattern="[a-z0-9._%+-]+@[a-z0-9-.]+\.[a-z]{2,}$">
                <div *ngIf="mail.errors && mail.dirty" class="invalid-feedback">
                    <p *ngIf="mail.errors.pattern" >
                        Formato e-mail non valido
                    </p>
                    <p *ngIf="mail.errors.required" >
                        * Campo obbligatorio
                    </p>
                </div>