Five Power Tips for Thunderbird
Since you mentioned Thunderbird extensions, I thought I would point you to my recent article on being productive with
Thunderbird: Five Power Tips for Thunderbird.
For managing mailing lists, I recommending using Gmane, which gateways them to newsgroups. This helps because news readers have features built around the large volume and impersonal nature of lists. Thunderbird has a decent-enough news reader built-in, so I use it. I explain a little more here, although that was written when I still used 'slrn' for news reading.