TB Menu Bar > File > Compact Folders. If you don't see the menu bar on top, press the ALT key.

Hi Ed, What does the Menu Bar look like and where is it? Nothing happens when I press the ALT key.

Edit Looked in Help and found the Menu Bar by clicking on a blank space,but most things under File, including Compact Folder, are greyed out.

Edit 2. So I need to select the folder first. Duhh!

Thanks. It always seems to me that things are hidden in different places on Thunderbird and you have to be an expert to find what you want

Hi Ed, What does the Menu Bar look like and where is it? Nothing happens when I press the ALT key. Edit Looked in Help and found the Menu Bar by clicking on a blank space,but most things under File, including Compact Folder, are greyed out. Edit 2. So I need to select the folder first. Duhh! Thanks. It always seems to me that things are hidden in different places on Thunderbird and you have to be an expert to find what you want

Not sure why 'Compact Folders' was grayed out; it should appear all the time. Anyway, it compacts all folders, not just the one you have selected. Did the messages stop after doing that?

Hi Ed, No, I'm still getting that message. Any more ideas?

I quite often get this message, though it tends not to be a problem later "Unable to write the email to the mailbox. Make sure the file system allows you write privileges, and you have enough disk space to copy the mailbox" One of the solutions seems to be Compact a File. How do I do this?

The usual diagnosis on this forum is anti-virus software. Are you using some? Can you create an exception for Thunderbird in it?

HI Rick. The main purpose of my antivirus is to scan emails, so turning it off doesn't seem a good idea. Also, the message comes and goes for the same email download - if I leave it, then try again, the emails download with no problem. However, the length of time to wait between attempts at downloads can be quite variable

Hi Ed, No, I'm still getting that message. Any more ideas?

Can also happen if you're getting multiple copies of the same message. If you think that's happening, go to your email via the web interface and delete that message.