Weird hover message

Every now and then, I come across something like this. It shows up after I have downloaded my messages using Thunderbird. If I hover my mouse to the left of the verticle line on the right in the screenshot. It does not affect anything, but I am wondering what it means. It is almost as if there is a hidden element there.

Hi @nathaniel and thanks for your message – and apologies for the belated reply.

This is a know issue (Error message "marked for deletion by an IMAP client" · Issue #544 · runbox/runbox7 · GitHub) and is probably caused by some email clients not actually purging deleted messages but rather marking them as deleted (when they for practical purposes should not be shown).

Do you typically purge deleted messages, or compact folders (which effectively does the same thing), in Thunderbird?

– Geir

HI @Geir ,

Thank you for getting back to me. All I do is check messages in TB. I checked the account settings, and the 2 options I have selected are:

1- Check for new messages at startup
2- Automatically download new messages.

Nothing else in TB is selected. I do not leave messages on the server and use POP as the server settings as I generally do not like to leave messages on the server.

I am not sure what you would call it, but I have 2 separate subfolders and I have TB configured with the username in the following format “” because I want emails to those subfolders to be kept separate and to show up on my phone separately. Otherwise they go to the folders with filters and I will never know when I get new messages.

I have a separate TB account configured as IMAP because when I send email from my phone or the web, it keeps the sent mail on the server. So now and then, particularly for important stuff, I will move it within TB from the IMAP account to the local folders in TB to effectively remove it from the server. I do not do that often though, and the hover message is from my inboxes.

For the few times I actually go to the IMAP box in TB, I never compact folders. I do not know what TB does behind the scenes though. I just keep that account tree compacted so as to not clutter my display unless I need to go into it.

I also get the following message sometimes from TB… I just ignore it because it gets the messages and they do get deleted from the server. It does not happen all the time.


I also get this “popup” message.

  1. Have webmail display only unread messages.
  2. Click a message. It will display in the reading pane and immediately disappear from the message list (which is a slight “problem” in itself).
  3. Hover over blank space in the displayed message.

This happens to completely new messages, not being flagged for deletion or read by another imap client.