Certain emails showing as invalid

Hello,

I use the Contact Form 7 plugin for our site (http://useleg.org). I have been told by two separate people that when they input their email address into the form, it says invalid email address. It is a valid email address, as I have had contact with them in the past outside of the contact form. They are school email addresses, so could that be an issue? They both have longer email addresses (Example: joe@scps.k12.fl.us), so could this be the problem? It is not recognizing it as a valid email, even though it is. If so, how do I fix this issue?

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