Multiple Emails separated by coma validation rule in Salesforce

Syntax:

1. OR(   
2. NOT(   
3. REGEX( Emails__c , "([a-zA-Z0-9._-]+@[a-zA-Z]+.[a-zA-Z,]{2,4})*")   
4. ),   
5. RIGHT( Emails__c , 1 ) = ","   
6. )