Rated 2 out of 5 stars
Incoming keywords are great but outgoing keywords might be equally or more important. Perhaps that could be included in the next version.
**Edit** After writing the review it did( barely) work on an outgoing mail. However, it failed to spot keywords and then accidentally created some by mistake. One of my keywords was "app" or "apps" and it started highlighting the middle of the word "happy" instead. I was able to remove the mistaken keywords from the body of the email but I was forwarding an email that had "happy" in the address and it was impossible to correct the mistake. It made it look like crap and I had to recreate the header manually. So it didn't work once, then it malfunctioned on the second mail and some of the mistakes could not be corrected. Not good!