title: regular expression to match all domain names except admin / www / mail
body: <p>I am new to regular expressions, but Give me this, I need to find a match:</p>
  
  <pre><code>a.com
  b.com
  c.com
  aa.com
  admin.com
  www.com
  mail.com
  vg.com
  </code></pre>
  
  <p>As a result, I have found a regular expression to all domains except the admin / www / mail.</p>
  
  <p>I wrote this:</p>
  
  <pre><code>[a-zA-Z0-9]+.com
  </code></pre>
  
  <p>But how to exclude admin, mail, www</p>
  
  <p>I tried this:</p>
  
  <pre><code>^(www|mail|admin)[a-zA-Z0-9]+.com
  </code></pre>
  
  <p>But it doesn't work</p>