Microsoft and a few other mail service providers have included a series of black-listed phrases/words in their mailservers which recently caused a few issues with emails due for our clients.
The problem stems from the following line in the grey/black list spam protection for the server:
These words are wildcard checked against the incoming mail server and rejected if found. Microsoft’s mail servers (bigfish) were submitted as co1outboundpool.messaging.microsoft.com.
A simple solution exists for those that have access to SSH. Run the following command:
# /usr/local/psa/bin/grey_listing –update-server -domains-whitelist “add:*messaging.microsoft.com”
This fix may well need applying after each plesk update depending on whether they alter this file.