2nd attempt to add screenshot

Have you turned off email scanning in your anti virus product? Most instances like this track back to the anti virus product in use.

Thanks for responding. Your suggestion does seem to imply choosing between stopping this problem, and having your incoming mail scanned. I have FYI been using the same A-V product (Avast) for at least 3 years and AFAIK these 2 (now) instances of messages downloaded again, never happened until recently.

I should also correct my original post. When I wrote 'the "unread" yellow asterisk' I meant the "New" yellow asterisk.

Appologies - entered wrong info - should be an answer to another question - I've got too many tabs open :)

Makes you wonder if this was some kind of reindexing done by AOL.

Pop mail accounts use a 'popstate.dat' file to keep a record of what has been downloaded in order to not download again.

Do you use a product like CCleaner or does AV product have capability of cleaning up files ? I'm wondering if the popstate.dat file was deleted or became corrupted and Thunderbird created a new one. Hence had no idea what had previously downloaded.

I don't use CCleaner or even have it installed. While Avast AV can clean up files it considers dangerous / suspicious, I believe I have to give explicit permission for that operation, but I will keep that in mind. Thank you.

Third instance. Now have turned OFF Avast incoming mail scanning and will monitor.

Defect occurred again just now. Contrary to advice (see screenshot), setting mail.server.default.dup_action to 2, does NOT move dupes into trash.

In 'Activity Manager' does it say the messages were downloaded.

Do you keep emails on the server after downloading ? If yes, can you logon to webmail account using browser and see if you actually have received more than one version of same email in Inbox. Please report back on result.

Thank you again! for lending a hand. I was totally clueless about the existence of Activity Manager. The attached screenshot shows that indeed 670 messages were downloaded (almost all duplicates) at 11:55AM local time. Curiously, a few minutes prior, Activity Mgr showed over 50 messages (without any downloads between 11;14 and 11:55) copied (as directed by a filter) to a separate folder. That is bizarre because almost all those copied emails were NOT in local Inbox, suggesting strongly that they were duplicate downloads.

I'll take this opportunity also to mention: 1. My A-V (Avast) still has scan of incoming email disabled. 2. My Android tablet, using Aquamail app, accesses the same POP account and has never had this problem of message duplication.

I notice all this activity is occuring in 'Local folders' mail account.

How many pop mail accounts (email addresses) do you have in Thunderbird?

How many pop mail accounts do you see listed in the left Folder Pane or do you only see 'Local Folders' mail account ?

If you only have one pop mail account, have you deliberately set it up to use a deferred Inbox ?

Is there any particular reason why you have selected to use a different Inbox instead of the pop mail account Inbox?

I have, and have always had (>10 years), 2 POP accounts, one foisted on me by Verizon, and the account I actually use. The former gets almost no activity. Both email addresses are and have always been, setup to put new email in Local Folders. I have no recollection of doing this explicitly and AFAIK this has never been an issue for me. There is ONLY a Local Folders root directory in the folders pane.

No idea what a deferred inbox is. In general I have tried to spend as little of my life as possible, customizing Tbird.

fredwehr said

I'll take this opportunity also to mention: 1. My A-V (Avast) still has scan of incoming email disabled.

With some anti virus products that is not enough, and in this case I would say it is not. Avast is a particularlyinsidious product and it has a habit of scanning all files before they are opened.

All references to whatever mail is stored on the server in a POP account is stored in a popstate.dat file in the profile (one for each account) However is for some reason this file can not be read (locked, corrupt missing etc) then all existing mail on the server is redownloaded as soon as you get mail. My guess is the file is locked by Avast trying to scan it.

Create an exception in any real time scanning Avast does to exclude the Thunderbird profile folder from it's actions. In the past we have seen Avast cause issues with individual files Thunderbird uses (msmail.tmp). I see no reason to think the product is not ny better at playing in the same sandbox with others. There have also been issues with Avast causing Thunderbird to hang.

Personally I question to quality of all anti virus products. Their invasive scope into the operating system often makes them little better than the things they are mean to protect us from. Common issues caused by anti virus are mangled attachments, missing images in mail, inability to send or receive mail and the redownloading of mail already on the server. The other big cause of re downloading mail is reindexing of the mail on the server which historically often happened when the server mail software was updated. But some providers like Yahoo have become positively unreliable in that regard, changing the reference number used on mail multiple time in a year.

2. My Android tablet, using Aquamail app, accesses the same POP account and has never had this problem of message duplication.

You have avast installed on your Android I am sure. https://www.avast.com/en-au/mobile

I do not know anyone outside of business that uses any android anti virus, but that has to do with battery life and processes sending the battery flat.

Thank you Matt. I'll try the Avast exclusion in a week or so after I return home. Have used paid version of Avast for maybe 5 years but I acknowledge they may have altered the app recently so it's a cause worth pursuing.

And yes indeed I have Avast on my Android tablet.

Just now, third or fourth occurrence. Screenshot of Activity Manager.

If it is not your anti virus it is your provider. I am seeing lots of issues with a couple of providers that all in some way link to Yahoo Be it contracted supply like the ATT customers have or association with yahoo/AOL.

As verizon no longer do mail, you are either with Yahoo or AOL. https://www.verizon.com/support/residential/email

With either of those providers, poor as they appear to be. POP is becoming impossible unless you remove mail from the server. Both promote IMAP and their decisions appear to only consider IMAP users, not POP.

Based on something else I had pointed out to me on an outlook forum, how frequently are you checking for new mail? apparently the longer between checks the less likely these sorts of things become, but I have no idea why that would be so, unless the server is actually so overloaded as to be swamped..

Thanks Matt for your continuing efforts to help; much appreciated!

Yes I am currently "chained" to AOL's mail servers. Tbird is configured to check for new mail every 15 minutes. I have investigated IMAP but am so familiar with POP, and used to having all mail on my PC (backed up by Mozy). I can imagine advantages to having all mail on a server but if indeed AOL is the culprit I wonder...

Regarding "unless you remove mail from the server" - at the moment Tbird seems to ignore the "leave messages on server" setting. I have it now set to 10 days but it's not deleting older messages from AOL. Have filed bug report on Bugzilla.

re: I have it now set to 10 days but it's not deleting older messages from AOL.

Do you compact the folders on a regular basis? Or Have you got these settings for that imap account: selected: Clean up (expunge) Inbox on exit? selected: empty Trash on exit? That would be in Account Settings > Server Settings bottom right under 'Message Storage'

1. Yes I have compaction enabled but run it when prompted. 2. Running POP, not IMAP.