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Have any one used this module? https://www.drupal.org/sandbox/guinness74/2396067
Nope - I've been using Rules with php to subscribe users to my lists when they create a new account. I'm then using a double opt-in to ensure that I'm not getting users in my lists who didn't intend to be there.
You can see this post that I wrote on this forum to assist you. It's not perfect, but works for me...
Drupal Sendy appears to have been abandoned - it's no longer possible to download it from that page. I found the original code on http://cgit.drupalcode.org/sendy and I'm using it as the basis for a new Drupal 7 version that will allow anonymous users to make double-opt-in subscribes (and unsubscribes) to multiple Sendy lists. I didn't have any requirement for the facility to provide a private list to Drupal site members, so I removed it entirely. I have it working nicely with the 2.1.2 API so far, and have responsive subscribe and unsubscribe blocks in Drupal. It's not quite finished yet, and currently supports 2 lists.
I don't have the time or coding skills to become a Drupal module maintainer, but if anyone reading this would like a copy when it's ready (probably in 2-3 days time) either for their own use, or to resurrect it as a full Drupal module, then message me here. It will need some work for general use, as I've tailored it for my requirements, but in a manner that is quite flexible. It's using a GPL2 licence.