"Unable to write email to the mailbox"

User Help for Mozilla Thunderbird

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Joined: December 27th, 2006, 10:27 am

Post Posted May 28th, 2017, 11:52 am

I have a very strange problem - maybe you could help me out.

I am using Thunderbird on 2 computers, both Thunderbird versions using exactly the same setup: occasionally I'm copying the profile directory from my main, standalone PC to the notebook computer (to have the most accurate email reply status information etc. there).
Now I've bought a new notebook computer to replace the old one - and on this new one, I now regularly receive popup messages like

"There was an error downloading the following message:
From: "Joan Brewster" <>
Subject: ***SPAM*** Re: C*alis Daily is worthy to try and to love.
This message may contain a virus or there is not enough disk space. Skip this message?"

When I click "ok", the message is skipped, otherwise I get:
"Error with account XY
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."

Note that the problem is actually NOT related to spam / a virus!
I get these popups even for normal emails of only a few lines and containing regular text.
And I seem to get them on a 'random' basis, i.o.w., some emails are processed without any problems, while others are not.

I am really curios about why exactly the same files (Thunderbird data directories) give me those errors on my new notebook, but no problems at all on my regular PC. Could it be related to the fact that my notebook only runs with a SSD disk? Also, the Notebook runs Win10, while the desktop PC is running Win 7.

It may be worth to mention that only 1 of my mail accounts (using a POP setup) is affected. It is a catchall account, meaning that sometimes when I didn't run Thunderbird for a few hours, 100-200 emails may have to be processed, many of which are to be moved to the Junk folder. Maybe it's a sync issue that is triggered in combination with fast (my SSD) harddisks?

thanks ,r.


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Post Posted May 28th, 2017, 5:41 pm

Moving to Thunderbird Support.

Are you running the same security software on both systems?
Is the new laptop now running a very recent copy of the data from the stand alone PC or has it been receiving messages directly from the server?
Also see this article -- ... he_mailbox


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Posts: 17
Joined: December 27th, 2006, 10:27 am

Post Posted June 7th, 2017, 9:55 am

Hi and thanks for your reply!

on my Win7 computer (where I never have this problem), it's MS Security Essentials,
on my Win10 computer (where I get these errors), it's the standard 'Windows Defender'.

On both computers, Mozilla's data files are on a SSD partition.

The KB hints:
I don't think the folder is corrupt, as I regularly sync the files between the computers. That has never been a problem. Compacting the folders also doesn't make a difference.
EncFS: nope (also in Win10, file compression or encryption isn't activated)
The old bug: I don't think this applies, because I'm using exactly the same version of TB and of the configuration files on both computers, so there's no difference in how they access the server.

My best guess is that it's either something about the SSD or some Windows 10 setting that causes the problems. :-(

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Joined: January 28th, 2017, 9:51 am

Post Posted June 26th, 2017, 8:39 am

I too am experiencing the "There was an error downloading the following message:", with final message about virus or not enough disk space, issue.

I seem to get this about every 20 to 30 messages, for just one message. It's also random as to what email message is flagged like this. (i.e. not a common sender). It has even flagged messages that are generated on the server, like Fail2ban.

I have "Compact all folder when it will save over = 21 Meg"

Running Windows 10 64 bit Pro/ Norton 360 (though does not matter if On or Off) / As of this date latest edition on Thunderbird 52.2.1 (32-bit) - POP3

Server - CentOS Linux 7.3.1611 - Postfix / Dovecot (Personal server in home).

Drive (C:) where messages stored locally is non-encrypted and has 1.6 TB of free space. Unlike Richey, I am seeing this on my two POP3 accounts.


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Posts: 121365
Joined: September 23rd, 2004, 8:57 pm
Location: Somewhere on the right coast

Post Posted June 26th, 2017, 3:51 pm

First, backup your Profile ( )

Create a new sub-folder under Local Folders. Move all of the messages currently in your Inbox to that new subfolder.

Confirm that you have made the recommended backup of your Profile.

Close Thunderbird and navigate to the \Mail sub-folder of your Profile folder. Delete both the file Inbox.msf and the file Inbox with no extension.

Restart Thunderbird and you should find a new, empty Inbox folder in place. Copy any messages you MUST have in your Inbox from the sub-folder created above to the Inbox. Compact the Inbox after those messages are copied in.

The "Real Fix" entry in this article -- also describes this process.

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