I thought the FAT32 files system was dead. Which is probably why you are having issues finding new occurrences. I doubt we even test on it anymore.

But that advice is as sage as ever. Unless you are running Thunderbird as Root, it does not have the permissions to change the setting.

I suggest you look here. http://askubuntu.com/questions/333287/external-hard-disk-read-only

Try those settings to fix your permission issue.

Hi Matt,

Thanks for taking the time to reply. Yesterday I decided to copy everything from that volume to another, in preparation for poking at it (maybe using gparted, etc, to recreate the volume). However, while copying, I found that one of the mail files was apparently corrupted (the error message indicated something about splicing, sorry, I didn't copy it down), and flipped the volume to read-only. After confirming this, I deleted that file and continued the copy; no other files presented problems, and it appears that, after rebuilding that account's mail, it's ok. I want to let it run for a few more days before I confirm that was the sole problem.

I probably should've run some utility to check for disk or file errors, but I didn't know the equivalent of chkdsk offhand, and no error messages pointed me toward a bad file (I did try doing "repair folder", but that didn't help).

I'll post in a few days (or sooner, if the issue comes back) so that if there is anyone else with this problem, they'll have a potential solution.

On a follow-up to your comments about FAT32, thanks for the heads-up about it. I'll have to research what to replace it with. It's 1 of 5 partitions on a physical drive. At this point, I can't remember exactly why I thought FAT32 would be the best option for the data drive - maybe I was planning to dual-boot this machine, or some such reason.

Thanks again!

waterfall-hunter said

I did try doing "repair folder", but that didn't help).

Repair folder reads the file and re builds the index (MSF File) that Thunderbird uses to populate the user interface. The name is perhaps a little misleading. It does no read data analysis.

After testing, it appears that the problem is resolved.

1 corrupt mail file - deleted and let the mail repopulate from the server.

This 1 corrupt file caused the entire volume to lock when it was accessed - whether by Thunderbird, or when I was trying to copy the volume (and that's how I found the specific file).

I feel bad that I thought it was Thunderbird... but because I had that account set to check for new mail upon startup and again every x minutes, I didn't "see" the activity that was causing the lock.