Hi; this is a solution and a question. I'm using Thunderbird Ver. 45.2.0, Windows 10 on a 64-bit Dell laptop, etc. etc. I have 2 school e-mail accounts that are based in Office 365/2016. In both cases, when I decided to untangle myself from any school and use Thunderbird instead, one mail acct. came in as POP, the other as IMAP. My other mail accts. are GMail and web-based for my websites. Turns out that IMAP [especially w/GMail accts.] DUPLICATES the mail; in other words, there are two Inboxes, one w/the GMail folders and one in the Thunderbird folder. As I fooled around w/the settings, there was a point where any mail written in Thunderbird would not even go out; it said the mail account wasn't authorized to send. I went back into the account settings and looked at the Copies & Folders settings. If you use the 1st option, for some reason it will then recognize that account can send mail. It also creates the appropriate folders for the e-mail acct. This worked for both POPs and IMAPs, and proceeded to import mail from the server up to a point, not all of it. Unfortunately, it does NOT get rid of the duplicate folders. IMAPs also run much slower than POPs. I guess my question is - how can I make Thunderbird go back and get those additional messages from the Exchange servers? And how can I eliminate the duplicate folder structures in IMAP-based accounts [specifically, the GMail]? Thanks in advance for your response. TechLadyNow