The more mails are in a thunderbird folder like "Inbox", the more the computer has to work to administer them. Wouln't it be advantageous to keep all mails as individual eml-Files within the operating system which need hardly to be changed once saved. Only index entries in a database like the current global-messages-db.sqlite might have to be updated more often. Furthermore, this saving mode could easier provide the possibility of opening the same email collection in a network from dfferent terminals concurrently, given that the index database be network-compatible.