Problems in receiving forms through email

I have a form here: https://www.fabiozardi.com/wedding-form

I create fields and all, I know how to do it…
But SOMETIMES emails don’t come, while in the Inbound messages I see the form has been sent. Is not happening every time: just sometimes. AndI have no problems with my email account (I receive the copy of the confirmation message for the customer, is from that email that I notice that the form has not been sent).

Could you please check and tell me how to solve this problem?
Thank you!

Fabio

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