title: using regexp to test for no special character or only numbers after `@` symbol in email address
body: <p>How can I test an email address to retrieve the following results:</p>
  
  <pre><code>mohamed_12@yahoo.com =&gt; valid
  9mohamed_12@yahoo.co =&gt; valid
  _mohamed_12@a123_a4.co =&gt; valid
  9mohamed_12@112344.co =&gt; invalid after @ only number
  9mohamed_12@_112344.co =&gt; invalid after @ special character.
  </code></pre>
  
  <p>The regex I tried to use is: <code>/[a-zA-Z0-9_].+(@[a-z0-9].+\.+[a-z]{2,3})/g</code></p>