From MozillaZine Knowledge Base

Before adding a setting to this article please verify using the config editor that the setting exists in either the latest release or a upcoming release. Many of the mail settings for Netscape Communicator 4.0 for example are no longer supported. This article was originally written using Thunderbird 2.* settings as the starting point, during the development of 3.0. So it documented a mix of settings from 2.*, 3.* and trunk builds.

Given the new "rapid release development process" it doesn't make sense to keep a historical record on what settings are available, or what the old default values were. Document whats used in the latest release or upcoming releases. However, please don't remove any settings that are ignored/no longer used by the current release, that information can still be useful in troubleshooting problems. Just identify them as being ignored, and what the replacement (if any) setting is.

Please don't add a setting if it doesn't apply to Thunderbird or other email clients built upon Thunderbird such as the open source version of Eudora. Don't add explanatory text about a settings different behavior for other applications. This isn't meant to slight Mozilla Suite or SeaMonkey users - the article is only meant to be a brief description of each setting, and adding application specific explanations and caveats adds clutter. Please add it in an article about that subject or a reference article instead. Tanstaafl 06:22, 12 September 2011 (UTC)

mail.prompt_purge_threshold

According to the main page, mail.prompt_purge_threshold defaults to false. In SeaMonkey 2.6a1 (equivalent to Thunderbird 9.0a1) the default is true, and I can't remember if or when it was ever different. I also don't know when Thunderbird and SeaMonkey diverged in this respect. OTOH, mail.purge.ask is still true by default in SeaMonkey 2.6a1, and the wording of the Compacting folders article seems to indicate that this is the "historical" value of the setting. — Tony 03:30, 12 September 2011 (UTC)

The problem is that this article was basically written for 2.* (with the occasional 3.0 specific setting added) while 3.0 was being developed, and I haven't updated a lot of it for 3.*, let alone 6.0. So many errors are due to it still having what was true when I originally wrote it. I updated the default for mail.prompt_purge_threshold to reflect current releases. I finally removed the advice to enable automatic compacting in the keep it working article last month. When I wrote that article in 2005 automatic compacting was not enabled by default.

mail.purge.ask still defaults to true in 6.0.2. The easiest way to confirm that (which I did) is to "reset" its value using the config editor. I'm wondering if Thunderbird now uses a different setting. I'll create a new profile and experiment, updating this article and the compacting folder article afterwards. Tanstaafl 05:44, 12 September 2011 (UTC)