Emails are being deferred with the message "550 5.7.1 Service unavailable, Client host [] blocked using Spamhaus."  for customers using: 

We have already requested a delisting with Spamhaus and took measures to remove the IP from the pool.


New messages being received by the SpamTitan US2 server will not be affected as we have removed the offending IP from usage. As per the previous emails that received the "550 5.7.1 Service unavailable" the senders were notified with NDRs and may attempt resending them.


08/04/2024 17:00 GMT+1 - The offending IP has been removed from the Spamhaus list and it is now service emails.