Thunderbird does not have 'Spam' folders. Pop mail account will have a 'Junk' folder provided by Thunderbird. Imap mail accounts will have 'Spam' folders because most servers use the word 'Spam' for that particular folder.

re :I have to search all messages to find out where the message has gone and it shows as in a Spam folder. It would be useful to see an image of that search saying it is in a 'Spam' folder.

Please note, Thunderbird does not add eg: [spam] to any subject line. Thunderbird does not use the word 'spam'. https://kb.mozillazine.org/Spam_warning_in_subject

Even email that have been 'marked as junk' by Thunderbird do not have the word [junk] added to any Subject.

If you have any Anti-Virus/Anti-Spam programs running on your computer, they will be scanning all incoming files which include emails and they can and do put 'spam' in the subject. eg: AVAST Antivirus: Additional Protection > Expert Settings

Some webhosts also provde Antispam protection on a hosting account which offer marking SPAM messages with ***SPAM*** in the subject.

The display of [SPAM] in the subject lines of some campaigns is being added by the receiving server's spam filter. Typically this occurs due to something the receiving server did not like about the campaign. https://support.delivra.com/hc/en-us/articles/115000352707-Why-is-SPAM-being-listed-in-the-subject-line-of-my-campaign-

Suggest you view the headers to see if there is a spam flag set and spam score. Select email to read and click on 'More' and select 'View Source' It opens in a new window.

RE: "Thunderbird does not have 'Spam' folders. Pop mail account will have a 'Junk' folder provided by Thunderbird. Imap mail accounts will have 'Spam' folders because most servers use the word 'Spam' for that particular folder."

I can assure you that a Spam folder does exist somewhere!

As I mentioned in my post, when I search for the message it shows the folder that it is in and it is called Spam, not Junk and I have to tell Thunderbird that it is Junk before it moves it into my Junk folder so Spam exists.

RE: "If you have any Anti-Virus/Anti-Spam programs running on your computer, they will be scanning all incoming files which include emails and they can and do put 'spam' in the subject. eg: AVAST Antivirus: Additional Protection > Expert Settings

Some webhosts also provde Antispam protection on a hosting account which offer marking SPAM messages with ***SPAM*** in the subject."

You can also see from the screenshots that neither my webhost, receiving server or even MailwasherPro have added Spam wording to the email and I confirmed with Bitdefender that their software does not do that either so something else is doing that when I receive it into Thunderbird.

The fact that Thunderbird shows these messages in a Spam folder shows that something is not right.

You mention 'Bitdefender'.

Bitdefender does mark [spam] https://www.bitdefender.com/consumer/support/answer/2158/ quote from Bitdefender "The email messages received from addresses in the Spammers list are automatically marked as [spam]"

You mention 'Bitdefender'. Bitdefender does mark [spam] https://www.bitdefender.com/consumer/support/answer/2158/ quote from Bitdefender "The email messages received from addresses in the Spammers list are automatically marked as [spam]"

I checked this before logging my issue on the forum as there is nothing in the Spammers list in Bitdefender.

I have attached a screenshot of an email which as I mentioned before, I can only find by searching emails and you can clearly see that it's location is Spam and the Junk folder is empty, so how can it be in a folder named Spam when everyone keeps telling us that Thunderbird does not create a Spam folder?!?

I have discovered that if I exit Thunderbird without moving the message from Spam to another folder, when I open Thunderbird the message has gone!

Your replies have not solved my issue yet but have prompted me to investigate other areas so thanks for that.

So I will do further investigation to see if I can get more information.

So let us have a lok here. 1. You are using a POP mail account. So Thunderbird will not have a spam folder. What the server uses is irrelevant as only the maildrop is polled for mail which becomes the inbox once it is downloaded. There are no folders server side in a POP situation. None at all. Everything folder related is local to the local machine. Simple as that. So unless you or some other software you have installed is using implementing a spam folder very badly, you don't have one.

2. Many mail server operators have spam filtering and in doing so some add words to the subject line like [SPAM], others just drop the message and say nothing. As your issue is related to a modified subject and a missing folder, SPAM filtering server side is most unlikely.

3. You are using mailwasher. Why I have no idea. I have tried to justify installing it for the last 10 years since I first encountered it on this forum. Folk having issues getting their mail kept mentioning it. But I really don't grasp it as having a purpose, and I really mean any purpose at all. I can see how it creates another pointless step in fetching mail and deletes mail you have read online and determined to be spam. But functionally I just don't understand why that is better done on something other than Thunderbird. In using Thunderbird to manage spam I am also training it's junk filter to better recognize what I see as spam.

4. You are using Kaspersky. Kaspersky Labs is a Russian multinational cybersecurity and anti-virus provider headquartered in Moscow, Russia. Can you trust them? Try running Thunderbird in Troubleshoot mode and continuing when prompted while you download another test. This should block the kaspersky interface. Still going somewhere but the inbox?

Have you tried ensuring these settings are disabled https://support.kaspersky.com/KTS/21.3/en-US/70766.htm There is a reason they disable them on version upgrades. It is a shame Thunderbird can't do the same thing.

Ok the search lists the email. Does it open it? it is possible to find things that no longer exist in searches, especially when the code behind the location is not an integral part of Thunderbird. If it opens, then it exists obviously.

One thing is clear. Thunderbird does not think the mail is spam. It's junk flag is not showing red in the list. Despite the messing with the subject line to say the message is spam, something Thunderbird has no capability of doing. So the issue is really a missing folder, or a third party product making a total mess in it's sandbox. Thunderbird has a cache of folder information in the profile folder in a file called foldertree.json. You might want to close Thunderbird and delete this file so the next start will be slower as the appropriate locations are scanned for folder files. That might locate a poorly created folder that was probably not created using Thunderbird at all.

It may also be your global index is corrupted. Perhaps it needs removing https://support.mozilla.org/en-US/kb/rebuilding-global-database

RE: Point 3 - I have used it for years without any issues and find it useful in grouping and sorting the many email accounts I have and it allows me to determine what I want to do with the emails (delete, flag as spam etc) and then only receive valid emails into Thunderbird...works for me.

RE: Point 4 - I don't know where you got the idea I am using Kaspersky, as the previous 3 replies mention that I am using Bitdefender!

Before I delete any files or rebuild anything, I have other investigations to do and hopefully they will resolve the mystery of the Spam folder but thanks for your reply, it's useful.

So let us have a lok here. 1. You are using a POP mail account. So Thunderbird will not have a spam folder. What the server uses is irrelevant as only the maildrop is polled for mail which becomes the inbox once it is downloaded. There are no folders server side in a POP situation. None at all. Everything folder related is local to the local machine. Simple as that. So unless you or some other software you have installed is using implementing a spam folder very badly, you don't have one. 2. Many mail server operators have spam filtering and in doing so some add words to the subject line like [SPAM], others just drop the message and say nothing. As your issue is related to a modified subject and a missing folder, SPAM filtering server side is most unlikely. 3. You are using mailwasher. Why I have no idea. I have tried to justify installing it for the last 10 years since I first encountered it on this forum. Folk having issues getting their mail kept mentioning it. But I really don't grasp it as having a purpose, and I really mean any purpose at all. I can see how it creates another pointless step in fetching mail and deletes mail you have read online and determined to be spam. But functionally I just don't understand why that is better done on something other than Thunderbird. In using Thunderbird to manage spam I am also training it's junk filter to better recognize what I see as spam. 4. You are using Kaspersky. Kaspersky Labs is a Russian multinational cybersecurity and anti-virus provider headquartered in Moscow, Russia. Can you trust them? Try running Thunderbird in Troubleshoot mode and continuing when prompted while you download another test. This should block the kaspersky interface. Still going somewhere but the inbox? Have you tried ensuring these settings are disabled https://support.kaspersky.com/KTS/21.3/en-US/70766.htm There is a reason they disable them on version upgrades. It is a shame Thunderbird can't do the same thing. Ok the search lists the email. Does it open it? it is possible to find things that no longer exist in searches, especially when the code behind the location is not an integral part of Thunderbird. If it opens, then it exists obviously. One thing is clear. Thunderbird does not think the mail is spam. It's junk flag is not showing red in the list. Despite the messing with the subject line to say the message is spam, something Thunderbird has no capability of doing. So the issue is really a missing folder, or a third party product making a total mess in it's sandbox. Thunderbird has a cache of folder information in the profile folder in a file called foldertree.json. You might want to close Thunderbird and delete this file so the next start will be slower as the appropriate locations are scanned for folder files. That might locate a poorly created folder that was probably not created using Thunderbird at all. It may also be your global index is corrupted. Perhaps it needs removing https://support.mozilla.org/en-US/kb/rebuilding-global-database

I have solved the mystery of the Spam folder.

In my searching around I discovered a Bitdefender Antispam toolbar in the Thunderbird Toolbars so I added it and looked at the settings available.

In the Toolbar Settings, Email Rules, there is an option to Move Message to 'Deleted Items' and if this is selected and Bitdefender thinks an email is spam, it adds the wording [spam] to the subject, creates a folder named Spam, adds the email to this folder and then adds the Spam folder to the Deleted Items folder in Thunderbird, so that explains why I could see the email when searching. There is also an option to Mark spam email messages as Read.

If you don't know the Spam folder is there and you close Thunderbird, the Spam folder is deleted and the email is lost which isn't good. I have checked all the settings in Bitdefnder Antispam and none of these Email Rule options are there so if you don't add the Antispam toolbar to Thunderbird and amend the settings you could be losing email.

I believe that these Email Rules should also be in the main Bitdefender Antispam settings as other users may not know about the Antispam Toolbar or even use it so I have logged a support issue with Bitdefender to see what there response is.

So thanks to Toad-Hall and Matt for your replies as it helped my discover more about Bitdefender and it's interaction with Thunderbird.

Thanks.

I think bitdefender should stop injecting stuff into applications they did not write and breaking them. If they did that I and others like me would not be wasting our time supporting bitdefender because the product has serious deficiencies. The developers are working to permanently block these "toolbars" and it can not come soon enough.

I totally agree.

I moved to Bitdefender from Kaspersky for obvious reasons but Kaspersky never had this kind of interference with Thunderbird.

Kaspersky handled Antispam functionality within it's own app and that's what Bitdefender and others apps should do...keep their functionality within their own apps!

I don't know if any other Internet Security apps affect Thunderbird in this way, do you?

Well most of them do something bizarre is my feeling. I am now using windows defender. Have been for a year without issues.

But;

Norton, Avast, LifeLock, Avira, AVG, ReputationDefender and CCleaner all come from the Gen Digital stable. https://en.wikipedia.org/wiki/Gen_Digital

The Kaspersky Anti-Virus engine also powers products or solutions by other security vendors, such as Check Point, Bluecoat, Juniper Networks, Microsoft Forefront,[68] Netintelligence, Clearswift, FrontBridge, Netasq, Wedge Networks, and others. Altogether, more than 120 companies are licensing technology from Kaspersky Lab. https://en.wikipedia.org/wiki/Kaspersky_Lab

I personally dropped ESET because I no longer felt I was getting value for money. It was unobtrusive is the best I can say about it.

I know nothing specific about Bitdefender, except it is like Facebook a personal fiefdom. In this case of Florin Talpeș a Romanian who started the company with his wife. Now following this thread, that it is one of those injecting toolbars.

Over the years this Thunderbird wiki page on anti virus programs does appear to have garnered dishonorable mentions for most of them https://wiki.mozilla.org/Thunderbird:Testing:Antivirus_Related_Performance_Issues#Problem_Antivirus_and_Anti-Malware_Packages And now including this. I have not edited that page in years, but others appear to be active.