tried again, different email. Getting similar error message, but more detail.
I'll try their customer support line this time.
I'll keep everyone posted.
This is an automatically generated Delivery Status Notification
THIS IS A WARNING MESSAGE ONLY.
YOU DO NOT NEED TO RESEND YOUR MESSAGE.
Delivery to the following recipient has been delayed:
groupbuys@bulkreefsupply.com
Message will be retried for 2 more day(s)
Technical details of temporary failure:
Google tried to deliver your message, but it was rejected by the server for the recipient domain bulkreefsupply.com by bulkreefsupply-com.20.amf2.atomicdata.com. [199.66.72.48].
The error that the other server returned was:
451 4.3.5 Server configuration error