How to activate tags in Mandrill


I have set up email marketing automation in Mailchimp and integrated it with mandrill.
I have a couple of emails send out in mailchimp (not in Mandrill) that should only be send in case the previous email hasn't been opened. Therefore I created tags and rules for these emails in mandrill.

Although emails have already been sent with a subject line that exactly matches the rule in Mandrill for the tag (if subject line matches 'subject x' the tag Y should be added), the tag still shows 0 in the tag overview in Mandrill. How is this possible?

Thanks for your help!!


Is this question about one of the exercises in this course?