Comment 7 for bug 2060534

Sounds like the Sent-1 file is so big it's not possible to do compacting maybe because either Thunderbird is interrupted during the compacting eg: shutdown, crash or receiving mail into the folder being compacted, maybe another program is scanning the file or it's possible that you might not be able to compact a large folder because you don't have enough free disk space or memory or there is some type of corruption in the file. 50GB is very large for a single text file and it looks like it's been failing to compact for a while, so is full of old deleted mail.

Does it say anything in the Error console ?
Open Error console (Ctrl + Shift + J') or 'Tools' > 'Developer Tools' > 'Error Console'
Clear Error console - top left bin icon

right click on 'Sent' folder and select 'compact'
If compacting does not work - Sent-1 is still 50Gb and nsmtp appears.
What do you see in Error Console - please post an image.

Either way you need a solution to overcome the current issue.

Suggestion:
- Create a new folder called 'Sent Store'.
- Move all the wanted sent emails into 'Sent Store' as a precaution to make sure you do not lose them.

So now Sent appears empty.

First try to fix Sent msf file:
- Right click on Sent folder and select 'Properties' - click on 'Repair' folder and click on OK.

then try to compact Sent folder:
- Go into 'Offline' mode to ensure nothing gets received into 'Sent' and then right click on 'Sent' to see if it manages to compact the Sent folder.

If it fails to compact and produces a new nsmtp:

- Exit Thunderbird
- Access profile
- Delete the nsmtp file and also the Sent-1 mbox and Sent-1.msf files.
- Empty the computer Recycle Bin.

Restart Thunderbird and the Sent files should get created.

It might be useful to keep the 'Sent Store' folder for all the older sent mail or Archive it or if you really want to you can move the emails back into the 'Sent' folder.

Please report on whether this fixed the problem.

> auto compacting - I dug through the settings now and was not able to locate it.

- Settings > General
- scroll down to 'Network & Disk Space'
- Under 'Disk Space'
- Is this checkbox selected 'Compact all folders when it will save over' ?
- What is the number of MB set ?
- Is this checkbox selected 'Ask every time before compacting' ?