Another good example of clear offer in email

This one is very simple, and you’ll see that the type is small and hard to read, but the point is that they are highlighting a promise of what you will get.

And:

In fact, notice that they are not highlighting the format, they are highlighting the outcome. “Weekly progress updates” is what you get when you sign up for their email.

Now, they also make this available by their website. That is a choice. Is it better to force people to read your email in order to get the updates? That is a different question. But again, I like the availability of the offer.