I have a lot of accounts (5) and I keep all my emails in local storage. My main accounts are configured in POP3 mode and my Gmail account is IMAP defined. At startup, Thunderbird is using already 450 or 500 Mb but even if initialization takes 30 sec, it works ok after that. Then with daily intensive usage and as I keep it open permanently, I can see that memory usage is growing up to a point where: System start paging and where Thinderbird GUI reacts with a big latency, forcing me to bounce the app. This memory leak exists for a long time now and as it doesn't seem to be identified I raise the point.