Self Service not generating ticket for specific user

Hello,

We have one user (That we know of) that the system is not creating a ticket for when he sends a request to our self service address. The logs show :

[12:54:14:606]|[08-11-2017]|[com.adventnet.servicedesk.mailutils.MailProcessor]|[SEVERE]|[125]|: Email is received from a new mail id : User@ourdomain.com. Configuration is set as NOT to receive email from new email addresses. Hence going to return null for user id.|

This is not a new user and they could create tickets without issue in the past.

Any thoughts or ideas? My concern is there could be multiple people experiencing this and we would never know.

Thanks
Josh