I'd suggest you move them to the Local Folders account, and split them by topic, context, date, sender, whatever, into many separate folders. Large numbers of messages don't seem to cause Thunderbird too much trouble, but huge monolithic folders do. The Archive function may be useful as it can re-file messages according to their age and preserving the folder structure, whilst also being searchable.

I'm curious about how you get into a position of having so many unread messages. I presume none of them are likely to be in need of urgent attention?

There's no easy way to take messages outside of Thunderbird and have them readily accessible. You can export them to a format such as HTML, or with a little effort, PDF, but you end up with a large collection of separate files with no logical connection between them. Following conversation threads becomes hard work.

Hi Zenos, Thanks for the input. To answer your 2nd 'graf first; I subscribe to large numbers of news collectors, Google Alerts, and other information sources etc., for my interests which provide much more information than I can read although, at some point it's my intent to read what's saved and further use them at some future, as yet undefined, 'stopping point'. Until then, they accumulate like snow on the roof.

To address your primary response; the 17.5K messages in archives are subsorted into many different sub files. The 11K unread e-mails are in a file under "Local Folders" which is subdivided into many subfiles by sender.

The e-mails I've read and choose to save go into a separate "Local Folders" folder which is also subsorted by sender. This folder is, however, archived annually to keep it smaller. This was prompted by getting the "Unable to write..." [attached] warning in the past.

I found that by marking all my downloaded e-mails 'read' and then 'compacting' them (a process I still fail to understand), I was able to download my e-mails without the "Unable to write..." issue popping up and stopping the download.

Now, as I try to download accumulated e-mails from similar files I made on Yahoo!, I'm getting this same warning ~ every 100 or so e-mails downloaded... the event that prompted me to post this query.

Are your scanning incoming mail with an anti virus? I suggest you turn that OFF

It is also probably a good idea to create and exception in your anti virus for your Thunderbird profile folder. You do not want the mail storage files locked by scanning while downloading. The message your getting is probably caused by a locked file.

Anti virus scanners take about 10 minutes per Gb of files. If you right click the folder and select properties you will see the size of the file on disk.

Lay-mans explanation of compacting. You have a task list with 100 items on it. As you work along you cross off the completed task. Normally the list gets messy and actually working out what has been done sort of gets lost in the cross offs. So you rewrite the task list with only the outstanding items. As far as Thunderbird is concerned, the same thing occurs, but instead of completed tasks it is deleted emails.d the rewrite is compacting

Note that I use Windows 7 and maintain a very messy Thunderbird where I fail to do much of the "good housekeeping" that we recommend to others. The result is.an 18Gb profile with nearly 20,000 files in it. My inbox has some 20,000 mail in it The folder that mail from this forum goes to has almost 35,000 email in it, and it is not alone, the largest folder is around 45,000 mails.

I mention this because many folk appear to think 10 or 20 thousand mails might strain Thunderbird. This is not the case. The only limits I place on Thunderbird is keeping individual folders under 4Gb in size and limit the number of messages synchronized in IMAP accounts. They are really more of a cache that a local store anyway.

Matt,

First, thank you for a very informative reply. It's good to know that large files don't 'gum up the works' in T-Bird and how to check file size. I doubt now, having checked several, that I have any even approaching 1 GB despite the large number of files I keep.

Two questions. First, I have AVG (free) anti-virus & ZoneAlarm (free) firewall. I certainly don't want to 'turn off my anti-virus' totally - which I don't think is what you meant, but 'creating an 'exception' sounds like a good idea... how do I do that?

You also say "... limit the number of messages synchronized in IMAP accounts...". I don't understand that - insufficient literacy. What are IMAP accounts, what are they synchronized to, and how do I 'limit the number'?

Again, thanks,