title: Exclude comma from email validation regex
body: <p>I need to improve a regex for email validator
  that is current regex I use:</p>
  
  <pre><code>'/^(\w[\+-\._\w]*@[-\._\w]*\w\.[-\w]{2,63})$/'
  </code></pre>
  
  <p>the issue is to improve this regex so it should filter emails like this:</p>
  
  <pre><code>"n,n@nn.nn" and "nn,nn@nn.nn";
  </code></pre>
  
  <p>First I have added a condition</p>
  
  <pre><code> (?!,) 
  </code></pre>
  
  <p>after 6th symbol so the regex become so:</p>
  
  <pre><code>'/^(\w (?!,) [\+-\._\w]*@[-\._\w]*\w\.[-\w]{2,63})$/'
  </code></pre>
  
  <p>this solved the first issue "n,n@nn.nn" but not helped with "nn,nn@nn.nn"</p>
  
  <p>so I added a new negative condition</p>
  
  <pre><code> [^\,] 
  </code></pre>
  
  <p>after 21th symbol so the regex became so:</p>
  
  <pre><code>'/^(\w (?!,) [\+-\._\w] [^\,] *@[-\._\w]*\w\.[-\w]{2,63})$/'
  </code></pre>
  
  <p>that solved both issues, but in such case validator fails on correct email if
  the first part of email (left side from @) is only one symbol like this:</p>
  
  <pre><code>"a@aa.aa"
  </code></pre>
  
  <p>Please, advice me how to work it out.</p>