I receive a "Unable to write the email to the mailbox" error message when check email in Mozilla/Thunderbird

Taken from a posting in a Mozillazine thread at


1. Delete some InBox emails. The specific number you delete probably doesn’t matter that much. I deleted 1000. Note the number of emails in the InBox after the deletion.

2. In Netscape, right click on InBox. Select “Compact this folder”.

3. When this is done, the InBox appears unchanged and apparently it is unchanged. But Netscape created – tucked in between the InBox and Sent folders – a new mail folder called “NSTMP”.

4. Left click on NSTMP. Netscape will automatically build a summary file/index and open NSTMP. You should see your reduced number of InBox emails in NSTMP. You may need to re-set your sort criteria to get it to sort the way you want.

5. Close Netscape.

6. In Windows Explorer, go to your Netscape mail files. Rename the InBox files to InboxOLD and InboxOLD.msf, respectively.

7. Rename your NSTMP files to InBox and InBox.msf, respectively. (You’ll see that NSTMP is smaller than 2GB).

8. Open Netscape and it will read your new, compacted InBox and allow you to get new emails. It will also show your InBoxOld folder but you can ignore it for now.

9. Once you’re satisfied that all your InBox email is there and you’re able to get new emails, close Netscape and go to Windows Explorer again. You can now delete the two InBoxOLD files.

10. When you open Netscape again, only your new, compacted InBox will be there and you’ll be able to get new emails.