An event registrant or donor that is filling out a form on your site has an email address with one of the fancy new "top-level" domains, and Soapbox is rejecting their form submission because of it.
Normally the top-level domain of an email address is going to be something we all recognize: ".com" or ".org" or ".net", etc. But recently, many new top-level domains have been introduced. Examples are:
If an email address has a top-level domain that is more than 4 characters, it will not pass Soapbox's validation rules.
We have a resolution to this issue on our product roadmap. When it has been completed, we will post an update to the Soapbox Updates forum.