re : 'Filter these messages'

This is refering to the 'Quick Filter Bar' which is ideal for searching for emails in a preselected folder.

Select a folder to view message list. Type any letter in the 'Filter these messages' text box. Below it will say 'Filter messages by: ' Please confirm that you have selected at least one of the options: 'Sender' , 'Recipients' ,'Subject', 'Body'. If none are selected than nothing will happen.

If you have selected 'Subject', and 'Body', but the search criteria refers to the 'Sender' who may not have typed their name in the email, then you will not find the result you are looking for.

If you have another filter option selected eg: 'Show only starred messages' and you search for an email which is in that folder but not marked as starred, then it will not find that email.

If you use 'Menu icon' > 'Find' > 'Search Messages' method, are you able to locate the emails ? You can select the folder on that account or the mail account. If searching the entire mail account, enable the 'Location' column header to see what folder the email has been located in. click on email

If it shows email in list, can you open that email. Does it show all content?

If you cannot select the email and open it either via the method above or via manual searching in folder: See if Folder needs repairing as index may be out of synch with actual emails in the mbox file. Right click on Folder in Folder Pane and select 'Properties' click on 'Repair Folder' button click on OK

Here is a detailed description of my version of the same problem on Thunderbird 52.6.0 (32-bit) on Windows 7 64 bit. When I refer below to the "quick filter window", I am referring to the window that shows the phrase "Filter These Messages ( Control + Shift + K )" on the quick filter bar, activated by the Funnel Icon on the Mail Toolbar.

One day, I sent a message to Foo Bar with an email address foo@raboof.com. Foo replied almost immediately, and I read the message.

A few weeks later I want to look at that reply again, so I typ "Bar" in the quick filter window with only the Sender button down. The message I want doesn't show up, though 62 other messages with the substring bar in the From address do show! After a very frustrating 10 minutes, I click the Recipient button and the message I sent Foo and BCC'ed to myself is immediately displayed. Since my Inbox is threaded, I expand the thread, and sure enough Foo's reply to me shows up, too. N.B.: I did not change folders or anything else!

It's not the threading, because if I unthread Inbox and repeat the experiments above, the results are exactly the same!

Furthermore, if I search for Bar in the search window on the Mail Toolbar, the message is not found, though lots of messages with bar as part of a name or subject are. If I search for Foo Bar in the Mail Toolbar search window, both messages are found. Searching for Foo or Foo Bar in the quick filter window does not do the trick unless I push down the Recipient button.

Interestingly, if I try the Menu-Icon scheme recommended by Toad-Hall above, the Find item is greyed out.

I hope that this careful exposition will convince Toad-Hall and others that this is not user error, and further that it will help the crack Thunderbird team find this BUG. I use the quick filter window all the time and rely upon it to find all the relevant messages.

re :Interestingly, if I try the Menu-Icon scheme recommended by Toad-Hall above, the Find item is greyed out.

If you have selected either the mail account name or a folder, then the 'Find' will be greyed out. You need to select any email in any folder to get 'Find' enabled.

The email you originally sent had this in the 'TO' field: Foo Bar <foo@raboof.com>

At the moment, I can think of two situations where the 'Bar' will not be located, so can you check these out.

When you received the reply did the sender Foo Bar use exactlly the same in the 'FROM' field. eg: Foo Bar <foo@raboof.com>

I have someone in my address book which I will call:

• First: Foo
• Last: Bar
• Display: Foo Bar
• Email: foo@raboof.com
• unchecked : 'Always prefer display name over message header'

So when I send the TO field looks like: Foo Bar <foo@raboof.com>

but when they send an email to me they use a slightly different name and my address book does not overrule it because the option is unchecked. So the 'FROM' appears as: Foo <foo@raboof.com> So a search for 'Bar' wil not locate it.

I also have a name for someone who uses an old email address with unmarried name, but I have changed the 'Display Name' to show the married name. eg:

• First: Foo
• Last: Bar
• Display: Foo Bar
• Checked : 'Always prefer display name over message header'

So when I send the TO field looks like: Foo Bar <foo@raboof.com> and when they reply, that 'Display Name' selection in my address book now overrides what they use. So I still see: Foo Bar <foo@raboof.com>

But in reality that person has used this in the 'FROM' field: Foo Boo <foo@raboof.com> The 'Foo Boo' hidden from my view because of my address book setting. But if I uncheck 'Always prefer display name over message header' or select the reply email from Foo Bar to open for reading. click on 'More' and select 'View Source' Check what is written in the 'From' field.

Does the reply email from Foo Bar actually say 'Bar' in the 'From' field?