This is one of those things that has changed. However, there is a "Subscription" option but it appears to be somewhat different from that of the past. Nevertheless, until I get that one figured out, you can still do what you want easily enough.
1. Go to your desired forum, e.g. Theology Forum.
2. Click on "Forum Options" and choose "Add Forum to Watched Forums"
This will then send you an e-mail that has any/all posts posted for the entire forum. Unfortunately, this has to be done for each individual forum and you will get individual e-mails for every post. I suspect that might be what you have enabled now and aren't happy with it, eh?
Soooooo, give me some time to find out what the new Subscription service is all about and how it works. When I find out more information about it I'll post back here. Change is good, Donkey!