|Are you||Then, try this|
|Sending TO and FROM the same email address?
Sending TO and FROM the same domain?
|Sending an email to a completely different address?||Look into having your recipient whitelist your email address, domain, or the IP addresses that your email might be sent from.|
Sending to yourself, from yourself, using an outside mail-server (in this case, Email Marketing) results in your filters thinking that your campaign is spam. It sees that the email is displaying your own address as the From Email. However, it also knows that the email did not originate from your own email provider -- the email technically came from our servers.
This can also happen if you're simply sending from an address at a certain domain, to another address at the SAME domain. For example, sending to firstname.lastname@example.org, FROM email@example.com.
Making an email that originated elsewhere look like it came from you is a common spammer trick. So, to protect you, most email providers have automatically added this pattern into their spam filters. Sometimes you can find the email in your spam folder, but sometimes it will be blocked, completely.