All of the discussions of our (discontinued) mailing list can still be reached under the following address:
https://geodynamics.org/pipermail/aspect-devel/
We will look into moving the discussion into the forum, but will decide this after an evaluation of the effort this migration would require. I will update this post when the evaluation is complete.
This post has been pinned for 6 years now. The old archives for the mailing list can still be reached under the link above, and they are still referenced in our Contributing guide, but I think it is time to unpin the post and free up this space at the top of the forum. The post will still be findable within the list of forum posts, just not at the top of the list.