Microsoft Office 365 encrypted mail message.html attachment) - ORF Forums

how do I blacklist all .html/.htm yet allow a legit message.html from microsoft office 365 ?

not really a solution. but at least it will allow you to block most of all other html attachments except those that are message.html and securemessageatt.html

^(?!message)(?!SecureMessageAtt)([a-zA-Z]+\.html)