I recently upgraded my open source store from v. 2.2.2 to v. 2.3.3. At that moment automated email replies (order confirmation, newsletter signup confirmation, etc.) began to fail. The emails are created, but they don't reach the customer, but fail with the following error:
host outbound.mailspamprotection.com [108.178.13.114]
SMTP error from remote mail server after end of data:
550 Messages should have one or no Content-Type headers, not 2.
For some reason, the Magento program is putting two headers into the Content-Type header. The email is returned to my inbox with the message:
This message was created automatically by mail delivery software.
A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed:
I have been unable to find any documentation or anyone else who is having this problem. I have had my Magento developers (I am not one) look at this but they have so far been unable to find the problem. Hopefully someone here can figure this one out.
Thank you,
John
