Just about everyone I have seen with this issue have a mail program on thy phone downloading mail and either it or their mail provider then marks the mail as read. Are you one of those?

Matt said

Just about everyone I have seen with this issue have a mail program on thy phone downloading mail and either it or their mail provider then marks the mail as read. Are you one of those?

I had thought about this, but here is the issue. We have 2 smartphones (iphone and windows phone) and a kindle. All of these devices get the emails along with my PC running Thunderbird. I did an experiment on some new unread messages. The smartphones both say unread until the message is actually opened on that device. The kindle and Thunderbird both loose the bold after a few seconds even with messages that have not been opened anywhere. One other point: I had to recently reinstall Thunderbird on my PC and move my old mail profile in to restore everything. This issue was never happening before the reinstall so something changed. Any thoughts?

I will suggest another more meaningful experiment.

Turn the two phones off and see if the mail in the other devices remains unread... I would say it will.

One thing is certain. This is not a Thunderbird issue. Not if your kindle is also affected.

I did try another experiment. Turned off smartphones and kindle. The messages remained not read (bold) on Thunderbird. Then I turned on the iPhone and as the messages download to the phone they turned to read (not bold) on Thunderbird. I conclude that Thunderbird should not do this. It should only un-bold messages if they are opened in Thunderbird. This is they way it worked for years before I had to download Thunderbird again to fix a big crash issue on my PC. Is there a setting in Thunderbird I can set to do what I want although this is the way it should work by default. Thunderbird should be independent of what happens on other devices.

Matt said

I will suggest another more meaningful experiment. Turn the two phones off and see if the mail in the other devices remains unread... I would say it will. One thing is certain. This is not a Thunderbird issue. Not if your kindle is also affected.

Thunderbird should be independent of what happens on other devices.

Sorry, no. Not if this is an IMAP account. A key feature of IMAP is that you can access your mails from several devices and they do not behave independently. It is designed so that if you read, edit or change your mail on one device, then when you access your mail from another device all your recent changes are reflected there. It doesn't matter which email client you use (Thunderbird or another), all of them behave the same.

If you don't want that behaviour then you need to set up your mail as a POP account, assuming that your mail provider allows it.

I suggest you read further to understand the difference. There are many guides on the internet, one of them is here: http://bt.custhelp.com/app/answers/detail/a_id/44934/~/what%E2%80%99s-the-difference-between-imap-and-pop%3F You will see it makes the point that if you are using IMAP and mark a mail as 'read', it appears as 'read' when you view it on another device: that is exactly the behaviour you are complaining about.

No,none of the above helps Before the last version update When I received a email,it was in bold print until I opened it Now It is in bold Print when I receive it 7 ALSO AFTER READING it I have tried everything I know,but nothing helps apart from right clicking the message & mark as read Please assist Thanks Darryl

This topic was resolved here https://support.mozilla.org/en-US/questions/1141135