If you use Gmail or Outlook/hotmail. it is simple. just change Thunderbird to use the local folder as those providers add the mail as it goes through their server to the sent folder (causes no end of trouble with duplicates and error writing to the sent folder.

Thank you, but this not resolve my problem.

Let's take a IMAP email, say seg@test.com Now we want to share this email for more PCs running thunderbird

PC1, thunderbird => IMAP => seg@test.com PC2, thunderbird => IMAP => seg@test.com

In this scenario the sent emails will be writted into "sent folder" of the IMAP email, so PC1 can see what PC2 have sent and vice versa.

But, for "purging" too big message list, I'd like to have, say on PC1, the SENT email added on a local email folder.

If you think how work "standard" POP3/SMTP, you will find that sent email is appended to "sent" file into "local folder" (or something) directory.

I hope this is a more clear request: write down (append) on a PC (local file, into c:\ or somewhere) file the sent messages of a IMAP email, PLUS the "standard" sent imap's folder.

Because, if you change the account setting, you can append send data in local file XOR imap folder, AFAIK.

I need "local file" AND "imap folder"

As I understand it, you are saying that: You server does not act like gmail, so copies are not auto put in Sent regardless, but need TB to specify where to save them. In addition, your server has some limitations applied to the server 'Sent' folder, where it deletes old messages automatically if older than eg: x days.

The result being that neither PC1 or PC2 can see the old deleted sent mail.

So, you require a copy kept on your PC in 'Local Folders' account, so you have continued access to previously sent mail even when the server has auto deleted them.

I can think of three methods listed in no particular order: 1.Manually copy: Synch for offline use, then select emails and use right click copy to and select folder in Local Folders.

2.Create a filter to work on manual command. If you perform this once a week you could set a second condition so you do not keep copying previously copied emails. Something like:

• Set to run manually.
• Match all of following
• If FRom is your email address
• Age in days is less than 8
• Perform these actions:
• Copy message to and choose a suitable folder in 'Local Folders' account.
• Select to run on 'Sent' folder.

Make sure the Sent imap folder has been Synchronised for offline use to make sure a full copy is actually in the profile folder. In offline mode, select only that filter name and select to run on 'Sent' imap folder.

3. Put an auto Cc or Bcc on emails you send using your own email address. This is set up in Account Settings > Copies & Folders' for the imap mail account.

These Sent emails would then be preceived as new incoming mail because you copied yourself into the email when sent. So they could be captured by the auto filters.

What makes these emails different from others you receive, is the FROM will be from your email address. Set up a filter to automatically run when getting new mail :

• FROM contains your email address.
• Copy Message To a suitable folder on Local Folders.

The problem affect big messages list (ex 10K) and big (>4GB/month).

I can simplify in those terms: how to save TWO copy of sent messages in TWO different position.

One is the "standard" IMAP sent folder (on the cloud via the provider), so can be viewed by other IMAP-clients; the second on a local file, to be archived.

It's possible to use (3), but I will not get the sent EML but a different one (a BCC). This is a problem during ERP software import.

basically you need to hire a developer to develop an add-on that does what you want.