Hey there,
To prevent email spoofing, if a person (whether guest or member) sends an email using the Contact form, the email should be sent from the server itself, not the From address. This will always land in Junk mail in major email services because there's no matching DKIM/SPF records for that email to be sent from the IP address of the server. IE: a gmail address is not signed on the Oxwall installation, so every email provider will flag this as spoofing, because anyone can enter anything in the "From" address.
Of course, this means we'll have to change the reply-to email manually when replying to this person, but it's better to do that than to have all emails land in the spam folder.