We have implemented API functions for that, but unfortunately they are not documented yet. With their help you can develop an user control that subscribes/unsubscribes users from/to the newsletter module. Please refer to this forum thread
for some more information about the APIs.
We are now working
on implementing such user controls out of the box. They will be available after installing the SP2
which is scheduled for the end of May
. Documentation for the Newsletter API's will be available with the same release.
Don't hesitate to contact us if you have other questions.
the Telerik team