Configure Exchange 2010 to Reject messages with Capitalised Subjects
Written on May 22, 2012

Upon receiving a few emails with their subjects entirely in capital letters, I wondered if I could defuse my extreme frustration at this situation using every Exchange admin’s best friend; the Transport Rule.

I was able to create the following transport rule to bounce/reject all messages with only capital letters in the subject, including ignoring the common indicators for replies etc.:

New-TransportRule -Name 'All Caps is Bad' -SubjectOrBodyMatchesPatterns '^(R[eE]: )*[^a-z]*$','^(F[wW]: )*[^a-z]*$','^(Fwd: )*[^a-z]*$'

This creates a new transport rule, and any message whose subject (or body) matches any of the following Regular Expressions will be bounced:

When a user tries to send a message with only capitals in the title, the following is returned. Note the 5.7.111 “Do not use a capitalised” subject bounce message.

This is obviously not something I recommend deploying in production, but it does show how easy it is to evaluate message bodies and subjects using regular expressions.


There's no commenting functionality here. If you'd like to comment, please either mention me ( on Mastodon or email me. I don't have any logging or analytics running on this website, so if you found something useful or interesting it would mean a lot to hear from you.