If your folders consist of just inbox, sent, draft, trash, a switch from IMAP to POP will put future messages on PC and no further action would be needed, other than copying existing sent folder to PC. If you want to just transfer some messages to PC, you could highlight and copy selected messages to a Local Folders folder, and then delete those highlighted messages from the server.

thanks david but how do I change my imap setting to pop to achieve the desired goal of removing the emails to my gmails server to my computer. thus reducing my storage needs. tia

First, create a POP account along side of the IMAP account. This will automatically download all messages in inbox to PC and delete from server. Second, install the importexport NG addon if not already done Third, highlight the IMAP sent folder, rightclick, select the importexport option to export as EML to a local Windows folder Now, Highlight the POP sent folder, rightclick and select importexport option to import EML messages and select that Windows folder If you now have everything for account now on PC, you can safely remove the IMAP account. When prompted to remove data, click yes.