question Sending email using privacyservice

Your email (an address you was sending from) is likely configured with some anti-spam technology, such as SPF (senders policy framework), this is done using DNS. Basically, the receiving server is checking whether your email arrived from legitimate mail server, which you use to send emails and which you (or your email provider) mentioned in SPF configuration. Now, if you are sending email to @ superprivacy .com, the privacy service is forwarding it to the real (hidden) destination email: somebody @ johndoe .com. The mail system used by johndoe .com will therefore find that your email was NOT originated from your mail server (determined via SPF), as it was in fact delivered via superprivacy mail server. No SPF match --> likely it is spam.