Issues and versions management has finally moved to Github.
A git mirror was already available for a few months and keeping both locations up-to-date required a lot of work.
Additionally, I realized using both systems than github's issues tracker was more simple to use than Redmine's one. It provides less functionalities but they are enough for Modoboa's needs.
Trac is a really good product but lacks of many interesting features (like the multi-projects one). Redmine seems to be a good candidate and is more simple to deploy.
The new project page is available here : Modoboa redmine instance.