I have a problem setting up Sing Up form related to a List.

I created a simple sign up form and use the URL link generated to load the form an insert data (email, first name, last name)

If I use as email address any address on google domain (google.com but also other domain registered on google server) the confirmation email was automatically marked as SPAM.

I think the problem is on the mail header generated by zoho.

If i send an email campaign to the same email address this one was not marked as SPAM by google.

Is there a solution?

Thanks

Matteo