
old data in large archive folders should not be indexed unless needed
When a new account is created thunderbird indexes all the folders. I have several archive folders with 20+ email. There is no reason to index this data unless forced to by the user opening or searching the folder. On my PC this takes 25%+ of the CPU. I did not measure bandwidth.
Shutting thunderbird down seems to stop the indexing. Better would be to index the "current" data. IOS email does this as does claws-mail.
I'm running FreeBSD 11.2 on CPU: Intel(R) Core(TM) i5-6300HQ CPU @ 2.30GHz (2304.11-MHz K8-class CPU). As I am a system/network admin, no great strain for me. For a geologist, etc would/could be an issue. Anyway it's always more efficient to do nothing