There are a variety of websites out there which will examine your domain's overall DNS health and report back with suggestions.
One of the most popular free tools is intodns.com. This website provides a comprehensive overview of your DNS health and offers suggestions for warnings or failures. One item is consistently incorrectly flagged, however:
SOA EXPIRE: Your SOA EXPIRE number is 360000. That is NOT OK.
This is safe to ignore (it actually IS OK,) even if the number listed is lower or higher. Other warnings may need to be investigated, and red failures absolutely must be looked into to ensure everyone is able to reach your website.
We are happy to assist you with determining what may be awry with your DNS health! Simply submit a support ticket anytime.