If you register a plugin step as PreOperation (Create or Update) for a certain entity that has activityparty fields (for example “To” of the E-mail entity), you’ll notice that your code modifications won’t apply for the activityparty fields you try to alter.
The solution is to change the Step Execution Stage to PreValidation and it will work for those fields too.
Also, thanks to David Jennaway for this post.
P.S.: Yes, it’s 2013 and we’re back on track 😛 Sorry for the delay, guys 🙂