HTML

Pre-fill the input with the default domain

you can append ng model value to the default specific domain available in span input group
<label for="inputEmail4">Email</label>
	<div class="input-group">
       <input type="text" class="form-control" autocomplete="off"
           id="email" [(ngModel)]="email" name="email">
           <div class="input-group-append">
               <span class="input-group-text pt-1">{{defaultEmail}}</span>
             </div>
    </div>