Several days ago, my friend had a trouble with his Thunderbird email client. He is a windows XP user and had used Thunderbird for several years.
Thunderbird showing an error that indicate the inbox folder is full so it fails to download new message. I have found the similar error with Microsoft outlook 2000 at one of my friend PC, since Microsoft outlook 2000 personal folder has 2GB limitation.
I ask uncle "Google" about this error... and I found that Thunderbird Inbox has 4 GB Limitation. But why my Thuderbird never show this error event my email size more than 4 GB?
By comparing the internal folder structure between my Thunderbird and his, I found the cause of error. My friend put all messages into inbox only and never separate or categorize them into folders in local folder.
And the solution come....
1. I close Thunderbird
2. I copy the inbox and inbox.msf file as a backup into other folder.
3. I open Thunderbird again
4. In Thunderbird, I make several new folder in order to categorize all inbox messages. My friend likes yearly categorization. So I make folder like this: 2011, 2010, 2009, 2008 etc, according to the year of each message.
5. I move all inbox messages into each yearly appropriate folder until inbox empty.
6. I close Thunderbird again
7. I delete the empty inbox file and inbox.msf file too.
8. I start again Thunderbird and Thunderbird will create a new inbox file.
9. I try do download new message but it still shows error message that Inbox folder is Full event actually the inbox file is empty at the moment.
10. I compact inbox folder and try to download new message again.
11. Finally it was working.
So,..it is better to categorize your email and separate them into each appropriate folder. I like to separate and categorize them by sender name.