First, I am NOT the person with the magic bullet on this, but posting a screenshot of your husband's input server settings pane may be helpful so viewers here will see the account settings. I presume his subscription settings identify all appropriate folders of the account. If unsure, please ask that he check. Certainly puzzling.

Thank you. And apologies for the duplicate thread (please ignore the other one: it was automatically created by something in the support system).

The settings should be as they are on this PC (mine), as seen in the two screenshots below, but I will confirm the settings when I have access to his PC.

In response to someone else's query on the other thread, the Thunderbird quick filter was not activated. It's just that all the emails stopped coming through, on all three accounts on his PC.

Thank you again.

Does he receive any error messages? Those would help. Confirming IMAP will also help. From your post, it seems everything used to work just fine, but suddenly not. Puzzling. I will see if I can locate someone who might have ideas on this.

Have you checked that View/Threads is set to All, and the Unread button on the Quick Filter (under View/Toolbars) is not active? Press Alt if the Menu Bar with View is hidden.

Hmm, I have to wonder, and that is never a good thing.

I looked here https://support.mozilla.org/en-US/questions/1504907 https://support.mozilla.org/en-US/questions/1500003 https://support.mozilla.org/en-US/questions/1452071 https://support.mozilla.org/en-US/questions/1352966

From which I discerned some at least of your accounts are hosted on Microsoft Exchange, you use BitDefender antivirus a known troublemaker and you use filters.

You talk about your husbands machine and yours and an assortment of apples best and probably most expensive products, but I have some issue with just how many email accounts are we talking about. You mention three Thunderbird mail accounts, and apparently at sometime in the future such will be offered. As of now however there is no such thing. So I think it is time to get down to tin tacks.

Who provides what email accounts? Do you and your husband and your phone share access to these three email addresses, or are there more than three? Do you still see these issues if you reduce your devices to one for a time?

With IMAP being syncronised, if you delete mail they will show as arriving in another instance, but probably into the trash folder as they have already been deleted.

Is there anything showing in the filter log that would indicate these missing mails have been filtered (and perhaps permanently deleted)

Can you confirm that email is configured on all devices as IMAP. That would be a very good starting point. I seem to recall some Apple devices had a penchant for POP, which does not work well when you are sharing email addresses across devices. Microsoft for instance ignore delete requests for POP mail and instead move it to a POP folder under the deleted items where it lingers forever.

Do you still see issues if you try running Thunderbird in the following manner.

1. • Does Thunderbird work as expected in Thunderbird troubleshooting mode?
   • Does Thunderbird work as expected with your OS started in safe mode with Networking. Instructions for each operating system: Windows 10/11, Windows 8, Windows 7, OSX

Note a wired connection is required to access the internet from Windows in safe mode with networking.

Thank you to all. I have been working through suggestions and think SFHowes may have cracked it. We have never grouped things by thread, so that is turned off in the "select columns to display" and when I go to View/Threads on the menu, everything is greyed out. I then activated 'Threads' and it showed that 'All' was ticked. But the point about the quick filter settings did make a difference. For some reason on one of the three inboxes the 'show only messages with attachments' button had been activated, and when I deactivated it eight messages appeared that had all arrived this morning. The missing older messages did not arrive. In the other two inboxes none of the buttons in the quick filter had been activated, but deactivating that one on the first inbox nonetheless seems to have solved the problem: eleven messages popped into inbox 2 (dated 7 April to today), and when I sent a test message to all three inboxes from my Gmail account, it appeared in all of them. So I am tentatively saying 'This solved the problem'. Renewed thanks!