I am setting up an existing IMAP account on Thunderbird, and synchronization is set to only sync the most recent 2 days. But Thunderbird is happily chugging along, downloading 90,000 message headers.

I have unchecked "Keep messages in all folders for this account on this computer" but Thunderbird seems determined to download all message headers regardless of date.

Is this a bug? Is it fixable?


This is not a bug but by design. The logic is to download all headers, so all emails will be visible. This way, when you attempt to read an older email, then TB can download the body and attachments for you.

The logic on which is based this behavior is extremely convoluted, and as usual in such over-complex cases, not very user-friendly and not at all common-sense.

The gory details can be found in the bug report
Bug 1564421 : Account setting "Synchronize the most recent XX days" not working.

  • So there's really no point in checking "synchronize the most recent x days" if you have unchecked "keep messages in all folders" then? – pbarney Nov 13 '20 at 18:55
  • This depends on your needs and if the way it works now is useful for you. – harrymc Nov 13 '20 at 18:56

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