HELP! Form won’t send when using a @gmail.com email

I have been using your plugin for many years, on many sites and have been very happy with it!
Until recently, when many of my clients started to get feedback from their users/viewers that people could not submit form(s). ?
So, I went in and tested and all was fine… UNLESS your email is ______ @gmail.com
?? What changed?
How to fix this?

Any form is rather pointless if you have a restriction on who can submit it.

Thanks! I hope this is resolved asap