Thanks for your replies.
Neil, your suggestion about sending just the URL of a hosted 'newsletter' is extremely clever. However, I'm not sure how it would work with sponsored newsletters, that one can read offline and would include the ad banners.
Shai, you're right: the eNewsletter module looks like the one I need. Please share with us any response from the developers. Regarding Zookoda, I'm actually a subscriber of several newsletters hosted there and it looks good. However, I'm not very comfortable with having to manage two separate subscribers lists.
Cog, I am aware of the subscription / subscriptions modules, which I'm using in other sites. However, they are not exactly newsletter systems.
Kind regards
---------------------------------------------------------------------- Albert Cuesta http://www.canalpda.com