I have been experiencing slowness in Thunderbird, specifically with the loading of messages. It does not seem to be associated with IMAP or POP accounts or whether the messages have already been downloaded to TBird. Single messages load relatively quickly. The problem is most evident when loading any message found in a thread. It can take 5-10 seconds to load an individual message and much longer when that message is in a thread. The longer the thread the longer it takes to load. Troubleshooting such as clearing the cache and turning off extensions have not resolved the issue either. What is odd is that if I use an extension to view the threads, such as Thunderbird Conversations, there is no lag. Any thoughts on how to correct this issue?