Try this site.
Regex Tester[
^]
Your regular expression:
^(\s*,?\s*[0-9a-za-z]([-.\w]*[0-9a-za-z])*@([0-9a-za-z][-\w]*[0-9a-za-z]\.)+[a-za-z]{2,9})+\s*$
Your test string:
bhuvan2001@gmail.com
If the Entered mail ID or contect is not matching then shows ["No Match Found"], so we have to change the expression to validate as per our requirement.
If the pattern & Entereted content matches, then it will display all possible values that can accept.