I have setup a new Mail Policy for outgoing and incoming attachments.

For testing purposes I have currently setup for outgoing attachment policy, allowed *.txt files.

However in this instance, when I try to send an email with a .txt attachment I get the following error.

"U nable to send message;Reason:554 5.7.7 Mail Policy violation : Check attachments and try again"

Also sending mails without an attachment also results in same error message. 

Can you help please.