I've upgrade my project to the new interface, and I do not find a way to remove two obsolete mailing lists (ogdl-chat and ogdl-basico). The intructions for doing this appear in other tickets, but seem related to the previuos SF UI.
Apache Allura: Tickets: #5660
Normally, you'd be able to do this via Admin -> Tools, then under Mailing Lists, Mailing List Admin, but for some reason, your Mailing List Admin page is returning an error. I'm escalating this to our engineering team to investigate: [allura:tickets:#5660]
Chris Tsai, SourceForge.net Support
Our engineering team as indicated this issue is resolved.