Oh boy, I fooled myself. I had "mailbox://<MyAccountName@domain>/Inbox?number= etc." on the clipboard and never copied it from an IMAP message. Sorry, forget what I said about IMAP.

So both my questions are relevant:

1. Can you send me the exact link (right click, copy link location) in a private message? 2. I also need to know where exactly the message is stored, so account and folder name. Maybe you use a global inbox shared with some other account?

Jorg, 1. Will do. 2. Folder for the current examples is always Inbox. (I believe it applies to other "destinations" for incoming mail as well, because I have a few filters to do that -- e.g., "Family".) These folders are not shared with any other accounts. In particular, Inbox is not shared.

I got the private message with the link: mailbox:// ... /Inbox?number=1179030417&messageid= ...

This absolutely staggering, a message number of 1.179.030.417, I inserted the dots for better legibility. So we have a little more over one (American) billion, that's like you received 1 message per second for the last 40 years and stored them all in the Inbox. E-mail only exists since the mid-1970ies.

So something is wrong with that inbox. Can you please compact and repair (right-click, properties, Repair Folder) that inbox. Once you've done that, please report back

(FWIW, I have been using email since the late 70's, but using TB and predecessors only since '95 or so.)

Compact: Size was 1.2GB before, 1.2GB after. Repair: Done. Now what? If I try to download, I'm sure this will succeed, because I have not updated from 52.0.1, which does not have the problem.

Now you can report the "number=xxx" part of the link here again and then you'd really have to try TB 52.2.1.

When you install it, you can install it into a different directory, say C:\Program Files (x86)\Mozilla Thunderbird 52.2.1\ and get another shortcut on your desktop.

You can run both versions on the same data with no harm done. So of TB 52.2.1 now works, we're cool, otherwise, you use TB 52.0.1 as before and we need to keep looking.

Will do. (New link has number=9546, at least in 52.0.1.)

No go: 52.2.1 still fails. ("number=7546", still.)

BTW, I "updated", which didn't give me the choice of a new location. (No problem for now: I'll just downdate to 52.0.1 again.)

9546 or 7546 is a much more reasonable, so you have approximately that many messages in the mailbox.

If you do a custom install, you can chose where to install and can pick a different directory.

I'm puzzled it still doesn't work. To figure out what's going on, I'd need a reproducible case on my machine to debug it, so I don't know where to go from here.

Well, one other oddity, if it helps: I had compacted the Inbox perhaps a month ago, or less. So the huge number of messages suggested by the old link did not represent an Inbox that had never been compacted. It represented one with about the same number of messages as now (yes, several thousand, but not more).

I've done a custom install of 52.0.1 to use for now, with the hope of updating the other (to 52.2.2, or whatever), with the expectation that a simple test will show whether the problem persists with the updated version.

For now: Is there an easy way to downdate my Lightning add-on to be compatible with 52.0.1?

Compaction doesn't allocate now message keys/numbers, only repair does. So the 1179030417 survived the compaction.

No later update will fix the problem since we don't have a bug filed for the problem yet. I can surely file a bug, but that wouldn't be actionable since so far only you can reproduce the problem. As I said: without being able to debug your case, I don't see how I'd fix it.

As for Lightning, hmm, that is a problem. When you remove the add-on, doesn't it offer itself again when you restart? If not, what happens if you search for Lightning in the add-ons manager? I know that different versions of Lightning can be a real pain when you use different versions of TB on the same profile.

I've done some more experiments.

If I change the user name in the account settings (server settings), then the message is not downloaded. If I also change the server name, the the "Download rest of message" link in the message really doesn't do anything any more.

So I'm wondering whether those messages got downloaded when different account settings were configured.

Maybe you should open another test account elsewhere, configure it with a download threshold and see whether the problem exists on a fresh account. Or try a new profile by starting Thunderbird with -p. That would also be done on a different account to avoid that messages get downloaded into the new profile and deleted from the server.

Understood about compaction/repair. Also about fixing the problem. I imagine I'll try each update as released, but without much optimism.

I'll also try re-installing Lightning in 52.0.1.

Lightning seems to work (in 52.0.1) now. Thanks.

I don't see how the user or server name could have been different, since (in reality) everything comes to a single one. And anyway, I'm using the same settings in 52.0.1 (succeeds) as in 52.2.1 (fails).

One question about the names: Does your experience with the changed names ("link... really doesn't do anything any more") exactly match my description of the symptom? I.e., status area shows the link, but clicking does not change that status, nor produce any visible evidence[*] that something is happening?

• Two things I haven't seen, perhaps because of brevity: (1) Perhaps the status area changes, but much too briefly (say, <10 msec) to be visible. (2) Perhaps the Task Manager or similar monitor would show a brief event in CPU usage, network traffic, or something else.

The essential point is that the status area must show "Loading message" and that stays for sufficient time to see it. If that doesn't show, then the link "doesn't do anything any more", which is what you're experiencing.

Let's look at the version history a bit. 52.0.1: works normally. 52.1.0: here we fixed a security bug that restricted access to some links in messages, sadly we broke the "download rest of message" link. We got lots of complaints. 52.1.1: We shipped a crude fix to the problem and complaints stopped. 52.2.0 and 52.2.1: We shipped a decent more sophisticated fix to the problem.

So while we established that the more sophisticated fix in 52.2.1 doesn't work for you, I'm really surprised that you claim that 52.1.1 with its crude fix doesn't work. In that version 52.1.1 we allowed (again) any mailbox: link in a message.

Sorry to ask again, but did you really test 52.1.1?

A fair question (though I don't think you asked it quite so specifically). A more specific answer, based on 2 items:

Item 1: About a month ago (probably 52.1.0), the download links stopped working. At no time since then have I had reliable downloads. So far as I can recall, I have not had a single successful download. It is possible, I suppose, that some large email to a less usual destination like "Family" succeeded a few weeks ago. (Certainly nothing more recent than that, however.)

Items 2: I regularly update TB within 2-3 days, whenever updates are offered.

This is the basis for my stating that the downloads were not working 52.1.1.

From what you explained previously, it should be easy for me to test 52.1.1, so I will try that now.

OK, now I've got a different problem (maybe worse?) with 52.1.1: The message I have been testing with apparently downloaded. However, it is lost. Details:

1. When I clicked on the link, "Loading message" status appeared. Then "Checking for new messages" and green status bar appeared. Eventually green bar went away. 2. That email is no longer visible in the Inbox, with or without its large attachments. 3. Also no longer visible on POP server.

I performed a Repair on the Inbox, but this did not help. I also did a search of the entire account's folders (based on the date and a word that appeared in the Subject line). That includes Trash, Junk, Inbox, everything. No luck.

OK, so despite what you claimed before, TB 52.1.1 "works" in that is shows the "Loading message" status message. That makes sense since as I explained in the "version history", the 52.1.1 has a crude fix which put it at par with 52.0.1.

So now we understand that the more sophisticated fix in TB 52.2.1 doesn't work for you.

Now to the disappearing message: I've seen this a few times. I've got a test message which contains status that when the message is displayed shows that "download rest of message" link. When I click that link, I get "Loading message" and then the message with the link disappears altogether because it is no longer on the server. That's due to the way I set up the test message.

So if the message disappeared from the POP server, any partially downloaded message with a link to the non-existent message will "auto-destruct" after showing "Loading message".

I hate to say it: TB 52.1.1 and TB 52.0.1 behave the same for partially downloaded messages, as does TB 45.8 or earlier. Only TB 52.2.1 has a more sophisticated approach and I'd really like to see a case where that fails which you had apparently, but now it's gone. Do you have a stack of those messages?

I suppose it is possible that I received no large emails during the tenure of 52.1.1. In contrast, I received quite a few several weeks ago, when I first noticed the problem, and many in the last week or so (far more than my usual intake). My statement accurately reflected my experience, but it may not have perfectly reflected my PC's capabilities at all times over that interval.

Yes, I've seen the disappearing-message problem before (starting many years ago, if memory serves). I used to be very careful about clicking that link, for just that reason. TB has become more reliable with time, so I have been able to relax.

In this case, I waited for many seconds (until a "Checking for new messages" message). I eventually tried again, because I could not be as trusting of TB as I used to be. Whether the 2nd click caused the loss, or it was already lost at that point, I cannot be sure.

I do indeed have several other examples. In which version of TB shall I try a download now?

I'll compile you a special version of TB with some added debug so we can see what's going wrong, OK?

Novel choice. Let's try it.