I use Mailgun exclusively for managing my email stuff. 10,000 emails for free and it gives you complete freedom, since you can program the events on your own. (That can be either a pro or con)
EDIT to reflect update: Maybe you can do something with the Mailchimp API? It's free for up to 2000 subscribers and it has possibilities of adding your own field, so you could create one for your tags.
I use Mailgun exclusively for managing my email stuff. 10,000 emails for free and it gives you complete freedom, since you can program the events on your own. (That can be either a pro or con)
EDIT to reflect update: Maybe you can do something with the Mailchimp API? It's free for up to 2000 subscribers and it has possibilities of adding your own field, so you could create one for your tags.