Because of an identity corruption problem, I had to create a brand new identity and re-synch all my mail with my IMAP Gmail accounts.  This all seemed to download fine, but on further examination, only the headers in Sent mail have been downloaded.  None of the messages are there.  If I click on a message header, it says Downloading .... and downloads the message.  So the data's there on the gmail server.  (I confirmed this by looking at the gmail account through a browser).  But I'm looking for a way to force it to download all the sent mail because unless it's been downloaded, it can't be searched.  Additionally, I can't tell if there was an attachment until the message has been downloaded.

Under Tools/Accounts - Advanced/Folders, I saw that the radio button for "don't save a copy of sent messages" was selected.  Why, I have no idea - perhaps that's the default for a new IMAP account?  In any event, I changed it to "Store sent messages in this folder" and selected Sent Items (Server).  It now seems to be saving sent mail there.

My question is, how do I get it to download all the prior sent mail (not just the headers)?  I tried Synchronize Now, and that didn't work.