Courier IMAP (4.15) stopped synchronizing moves after ~~Play Store~~ F-Droid(?) updated me to K9-12.1

[binki]

I noticed that K9 stopped being able to synchronize email moves to my IMAP server. This happened on both of my phones. Desktop Thunderbird isn’t affected. I see that Play Store updated K9 to 12.1 this morning. I don’t know how to tell what version I was using before that.

I don’t notice this issue with Office365 (Outlook/Exchange?).

I am running an outdated version of Courier IMAP (4.15).

The change log I see in the Play Store is just:

• Selected/read/unread message states were hard to distinguish visually

Was there some other change related to the IMAP protocol that landed too or in another recent version which Play Store skipped? Does anyone else using Courier IMAP or some specific ISP mail have a similar issue?

I do know I need to update my Courier installation, but I also want to know if K9 has a compatibility issue with the latest version of Courier which needs to be investigated.

[binki]

It looks like this is documented at Folders on IMAP servers with prefixes are completely broken since 12.0b4 · Issue #9567 · thunderbird/thunderbird-android · GitHub with a confirmation that it is a regression of K9 which affects all versions of Courier and workaround. Note that after applying the workaround, you have to wait for K9 to notice the updated folder names before moving will start working again—once you see “INBOX.” (actual namespace will vary depending on server setup) prefixing every folder name, moves should start working again.

NOTE: you must reconfigure all of your special folders (Junk, Trash, Outbox, Archive) manually after K9 notices the namespace too.

[Zeroid]

@binki, Did you mean F-Droid rather than the Play Store. Version 11.1, not 12.1 is showing on the Google Play Store for both K9 and Thunderbird.

[binki]

I do have F-Droid installed on my phone, so that is possible. But I got the version number and installation date/time from the Play Store app. Does the Play Store app show installation dates and times for apps it doesn’t itself update?

When I look on the Play Store website, it seems to refuse to show things like version information.

When I look at the app’s listing on the Play Store app on my phone, it shows both version 12.1 as the app information (with a release date of 2025-09-03 even though I only received it last night) and it shows separately that the version I have on my devices is 12.1. Is the Play Store app being misleading when it shows that 12.1 is the version of the app there—is it getting that information from my phone instead of the Play Store?

[binki]

Ah, I finally found it. When I am logged into Play Store, the website moves the reviews above the “About this app” section. So I had to use a private window (where the “About this app” section came before the reviews). I never expected it to be beneath the reviews and I didn’t know what the heading was called so it took me a while to locate it. It does look like it’s listing only 11.1 currently.

[binki]

But this is quite confusing because the Play Store Android app literally shows “12.1” in the same Version field which the website displays “11.1” for (i.e., not in the device-specific section):

Website for comparison: