Badges
Accepted Solutions
Likes Received
Posts
Discussions
Ideas
Blog Posts
There's lots of articles and discussions on this on the community when I just searched.Here's one: Handling Multi-Select Fields in Salesforce
I don't think email scripting tokens work in subject lines.Try placing that in the body of your email and see if you still get an error. If not, you will know it's the location that's the issue.