We're trying to implement a rule on certain mailboxes that it shouldn't accept an email without a subject.
I found documentation from Microsoft on exchange 2010 to Configure
a Transport Rule for Messages That Have a Blank Subject, but I tried using the ^$ RegEx
with Exchange 2013 and it doesn't seem to work.
I also looked at the Transport
Rule Predicates for Exchange 2013 and it clearly says thatSubjectMatchesPatterns
matches messages where text patterns in the Subject field match a specified regular expression.
My workaround was to reject all messages to those specific mailboxes except if subject pattern matches. but
if I want to add now conditions ie. to reject emails with a subject "Sent from my snipping tool" I can't do it.
I found Here that
Exchange 2013 now supports extended RegEx but I didn't find that the syntax for ^$should
be any different in extended RegEx.