lets just try bypassing the massive overheads of an IMAP move.

use the import/ export addon. https://addons.thunderbird.net/en-US/thunderbird/addon/importexporttools-ng/?src=ss

once it is installed, right click the inbox and importexporttools and from the following folder choose export folder. pick a location and note where it is. navigate to Local Folders and create a folder to hold you exported mail. Select it and right click, Select import mbox file and set the import to the file you just exported.

Once that is done and you have check a few of the imports that they are complete messages, return to the folder you exported, select all mail (ctrl+A) and press the delete key. to delete al mail.

This is a little convoluted, but more reliable and much faster than trying to move the messages within Thunderbird.

Thank you so much for your reply to this. I really appreciate it. The delay in getting back to you is that I have been trying to do this.

I tried export folder and it only exported a couple of emails and did it pretty much instantly.

So then I tried "Export all messages in folder/eml format". This appeared to be working and I have a folder with eml files in it. However, yesterday morning I checked and the number of emails in the folder was 5380 where there are a total of 41,555 emails to export in that folder. It is the same time the next day from that again and the number of emails is still 5380.

Thunderbird shows a little red "stop" button with a tooltip "Stop the current export". I'm not convinced it's doing anything now though.

What would you advise please?

Thanks SO much!

Dougi

I think the process is either dead or stuck. Due to a bug :) got to love them, restart Thunderbird and right click the relevant folder and select compact. then again right click and select properties and then he repair button.

Open the Activity manager and watch for the account and indexing to end. Then try again. My export of an MBOX file took perhaps 10 seconds, as the current mbox files was copied to the export location, where as export to EML requires each mail to be extracted and copied one at a time. Exceedingly slow and seriously prone to the ravages of anti virus programs scanning all the disk activity.

The repair will resync the contents of the folder, so it should not be such a hit and miss, I am assuming that the existing folder has got some holes in it.

Oh and please check the folder is syncronised in account settings >synctonisation and storage. you can't export what is not downloaded.

Thank you, that's very helpful indeed and greatly appreciated. I'll try that now :)

One relevant item I have noticed is that Thunderbird is extremely slow in moving messages if the number of messages selected to be moved is 40K or above and selected via a method that can select only part of the messages in the folder.

Try selecting just one message, then entering a control-A character to expand the selection to all messages in the folder.

Personally I would expect total failure and data loss moving more that about 500 messages at a time. Not slow, data loss type failure.

I suggest you look at using the Ctrl and Shift keys in conjunction with your mouse.

Ctrl + A selects all Shift selects all between the current selected item and the second item selected with the mouse. Ctrl allows the selected / unselected state of individual list items to change based on their state when clicked.

These are operating system shortcuts that most people are simply not aware of, so they look for tick boxes on lists.

That could be - the folders I was moving large numbers of messages between were all local folders, not an IMAP folder.

I have been using Ctrl and Shift keys for years now for local folders.

milesrf said

That could be - the folders I was moving large numbers of messages between were all local folders, not an IMAP folder. I have been using Ctrl and Shift keys for years now for local folders.

It is the IMAP overhead that makes the thing a bit of an issue. Local folders have to overhead in "chatting" to the server to keep things synchronized. I don't know what goes wrong, it might just be that the cache fills up, or gets so large that the code can't properly address the locations. There is no hard and fast rule as to when things go pear shaped, just that they get unreliable somewhere around a thousand. Never really used to be a problem when mail accounts were limits to 5mb per account by providers.

Having anti virus scanning active in the profile folder certainly increases the risk of failure, as does an unstable internet connection and lots of other factors, not of which apply to "local folders" account folders, or POP folders in general.

Hi Matt. Just a quick note to say that after a few days of processing, all the emails now seem to have been successfully transferred to my offline backup folders. The trick was to have the mailbox sync to offline. Once that had completed, the export worked fine and I was then able to import it into my offline backup folders without issue. It took a few days, but worked perfectly (I think!).

Thanks so much again for your help. It's been greatly appreciated.