He asked for an example of a web service that doesn't follow the RESTful model. I replied to his request. My point is that almost no web service is truly "RESTful".
Sending email is best mapped to POST (create), not PUT (update), and the URL doesn't change for POST.
What I find annoying is people objecting to "POST /actions/subscribe" (with the params in the post body) because it's "non-RESTful" -- the url is a verb and REST demands a noun.
That way you can list your subscriptions, modify, delete in a very consistent way, without a need for "POST /actions/modify_subscription" and such.
POST /actions/subscribe
and POST /subscriptions
and POST /abcdef1234567890
The shape of a URL has nothing to do with REST. However, if a lot of your URLs contain verbs it suggests that you aren't doing REST. It's a design odor.