Conditional Email Not Sending to One Address

We use conditional logic to email submissions to the appropriate employee.  Suddenly, one of the five recipients is no longer receiving emails.  The other four are still receiving emails.  All of the addresses are on the same domain, and @jotform.com is whitelisted in our mail security software and the submissions are not in her junk mail folder.  We have not altered the form in over a year, and we have not hit our submission limit.  Within the submissions to this particular email recipient, all of the necessary information has been entered correctly. The form is located on a private intranet, so I cannot submit the link.  Any ideas on what else can I do to troubleshoot this issue? Thanks for any suggestions you can provide.

Edit: I have seen in other questions that some emails can land on the "bounce list."  Is there a way for me to check if any @eastgreenbushlibrary.org addresses are on the bounce list?  As I mentioned above, JotForm's domain is already on our whitelist.  Thanks!

Ye, here is how to check and remove if the recipient email went to bounce list: https://www.jotform.com/help/262-How-to-Remove-Your-Email-Address-from-Bounce-List 

Let us know if you need more help.