Imap. You should subscribe to see the server 'Sent' folder which may be called 'Sent' Items' or 'Sent Mail' etc. Right click on mail account in Folder Pane and select 'Subscribe' select 'Sent' folder and click on 'Subscribe' click on OK

Some servers auto save to the 'Sent' folder in which case you do need to save it as it will create duplicates. eg: Gmail.com and I think hotmail.com both auto save any sent email.

Right click on mail account in Folder Pane and select 'Settings' Select: 'Copies & Folders' for imap mail account

If imap server is auto adding sent copies, then do this: Uncheck: 'Place a copy in' In other words, do not select to place a copy in Sent.

Usually you would select the following for imap: Select: 'Place a copy in' Select: 'Other' and choose the Sent folder on the imap mail account.

click on OK

Toad-Hall " Thanks for your answer. I have correctly setup of Sent' subscription folder. When I send mails without attachements or with attachements but very low weight < 4MB. Everything is fine. Mail is sent properlly and sended copy is in 'Sent' folder placed (only one message).

My server can't doing auto copies. When I turned off 'Place copy in - sent folder e-mail inbox' this copy is not making.

I suppouse something is with connection time limit. Maybe this scenario is true... TB is trying to copy sent mail to the 'Sent' folder but during this operation time limit has been reached... so TB is trying once again and then... return error... nevertheless mail has been sent and copies are made in 'Sent' folder - it makes sense?

Have you tried disabling outgoing email scanning in your anti virus product?

I don't have antivirus on that computer.

It has to be something with communication limits more than internet speed. You do send 4MB e-mail to the recipient and then repeat the operation of sending that e-mail to your Sent folder in the IMAP server. That is really wrong.

And you mention that you get this message: "Error occur during saving messgae in to Sent folder. Do you want to try again?"

Definitely something you should check with your e-mail provider.

It would be better to try make the Server create the copy on its side and you not having to do it twice.

Maybe after the error, TB tries again, and it puts a second copy of the Sent message in the server (even when the first did work and it got an error message)

If not, just try another provider, Local ones are always messy because they know less than you and overcharge.

iampowerslave thanks for an answer.

That lokal provider is not so small. ;) I'm not convinced about provider problem because at home this problem doesn't exist. But at home I have different ISP provider and router.

I suppose that problem is with connection or with router.

I was wandering is any chance to change timeout in Thunderbirt. I found information to change something like mail.mail1.server.timeout... in advanced settings. There is value 29 but i don't know is that minutes or seconds. When i change it to 300 mail has been sent properly but when i wanted to check this value again was 29 :/ So i'm confused is that probe with sending message properly was coincidence or is value changed always when you tried to go in adavanced settings.