Does the same happen when you run Thunderbird in "troubleshoot mode"? https://support.mozilla.org/en-US/kb/troubleshoot-mode-thunderbird

I just entered thunderbird in troubleshoot mode, and then asked it to compact folders, and the not read flags were not reset. That presumably means that one of my add-ons is causing the not read flags to get reset. In fact, the not read flags are not reset on my laptop in thunderbird, so maybe a comparison of the two can help with my problem.

Do you use Bitdefender and did you install the Bitdefender antispam toolbar in Thunderbird? Bitdefender toolbar is known to cause this issue https://community.bitdefender.com/en/discussion/89274/bitdefender-anti-spam-toolbar-causes-thunderbird-to-ark-all-incoming-emails-as-read?tab=all

No, I don't use Bitdefender. I use the windows built in security for anti virus and other protections. I also don't use the Bitdefender thunderbird add-on.

So Bitdefender is not the culprit. I cannot find the cause for you since the issue doesn't happen on my computer. Please read carefully the paragraph "The problem no longer happens in Troubleshoot Mode" https://support.mozilla.org/en-US/kb/troubleshoot-mode-thunderbird#w_the-problem-no-longer-happens-in-troubleshoot-mode

How do I contact the developer of the add-on that caused the problem? I see no email address for the author of the full address column add-on.

The developer of which add-on?

The Full Address Column add-on.

Are you sure that the Full Address Column add-on is causing the issue with your unread flags? Which would mean that if you disable this add-on the "unread" icon is displayed correctly?

I just know that I enabled the add-on and had new email and compacted folders and the new email was no longer marked as unread.

Unfortunately I am not able to find a solution for your problem.

As it turns out, I have mislabeled the flag for messages that I was referencing. It is not the not read message flag, but is instead the new message flag that is getting reset by the Full Address Column add-on. Sorry for the confusion my mislabeling has caused. I have discovered how to email the add-on developer and am now composing a message to him about this situation.

The 'New Message flag'

Please note: 'New' means new since you last accessed the folder.

If you start Thunderbird and new mail is downloaded to eg: Inbox, then the Inbox folder should turn blue to indicate new mail and when you select the Inbox, all 'new' mail should have a four pronged star just before the Subject. As all 'new' mail is unread then they will also be marked as unread and bold.

If you selected that Inbox' with 'new' mail, but decided not to open anything - instead you selected another folder - when you do back to the 'Inbox' all the 'new' marks will disappear because there are no 'new' mails since you last accessed the 'Inbox', so they all are now just 'unread'.

Compacting should not effect that new setting unless you selected another folder and then reselected Inbox.

You mention an addon : Full Address Column add-on Is there a reason you choose to use that addon ? I'm presuming you want to see full email address in the 'From' column header ?

That option is now available in Thunderbird.

• Settings > General
• scroll down to 'Message List' section

Select prefered option - there are three options

1. Full name and email address
2. Email only
3. Name only

So you could uninstall the addon if the settings I mention above offer what you desire and sort out the 'new' issue.

Can I set the full email address for the "From" column for only the spam folder?

I can understand your reasoning on this, but the 'Settings' > 'General' options are global settings - not per account and not per folder.

I suppose as not all junk/spam is correctly put into the Spam folder, it means you can see that information in any folder.

However, as a word of warning, the bad people who really cause a nuisance, will not display their email address in the From, so it's not exactly helpful in that respect. You cannot rely on what the sender has put into the From. You may even find some that seem to have sent by you :) Sometimes, you can detect the email address in a 'Reply-to' that got included (you would see that in the Message Header when email is selected) and sometimes you can only check to see if person is using an IP address of a VPN via the headers. So. you can opt to display data in the Message Header area.

• Select any email and click on the 'More' button in Message Header area.
• Select 'Customise'

There is an option to display senders full email address and also you can enable to show full headers - even if you only need to see it temporarilly. The best way to view headers is via 'More' and then select 'View Source' which opens in a new window. The top Received by headers are your receiving server for your mail account, as you work down the headers, you are working back towards the original Received by server and it may mention the IP of original sender. Then you would need to check whether the IP is via a VPN.

Many bad emails rely on the user doing something silly, such as being curious about an attachment when they know it's probably bogus based on the email content. Thunderbird by default does not allow remote content, so any remote content even from tiny invisible icons would not be enabled. Never click on a link - always hover over link and look in the bottom status bar for the real link information. But if you do not allow remote content, do not let curiosity get the better of you, do not open attachments without knowing who sent it and do not auto click on links before you know what you are clicking on - then simply opening an email to see Header data will not cause any problem.

I think the situation here is pretty simple - the problem is "This add-on asks for full permissions because there is still no official API for manipulating columns in Thunderbird 115+ and implementing custom (experimental) API bypasses all permission checks. DO NOT USE THIS ADD-ON IF YOU DON'T TRUST IT." from https://addons.thunderbird.net/en-US/thunderbird/addon/full-address-column/

You will likely have trouble with many future Thunderbird updates as long as you are using the release channel version of Thunderbird.

Good advice for users in similar situation is to change Thunderbird back to ESR channel. Instructions at https://support.mozilla.org/en-US/kb/thunderbird-release