Does anyone know why this happens?
The error sent to my smtp server email is:
Delivery has failed to these recipients or groups: Created By The format of the email address isn't correct. A correct address looks like this: firstname.lastname@example.org. Please check the recipient's email address and try to resend the message.
But "Created By" is a variable. It shouldn't be in an email format. Also, last I checked, this variable has a name inside. It's not empty.