64 bit Windows 10 Home addition, Thunderbird - Ver. 52.5.2 (x86 en-US) updated 01/05/18, Firefox v- Ver. 57.0 (x64 en-US) -system shows Firefox last updated 11/15/17. My PC has been wanting me to update Firefox, but I was telling it to remind me later for the last 2 or 3 weeks. I shut my PC down. 5 days later I turn my PC on, waited for it to boot, then started Thunderbird which automatically downloaded my last 5 days worth of emails from the server. My PC then froze. Eventually I powered down my PC and turned it back on. After it rebooted it asked me to sign in to Firefox to sync my devices. (I am assuming that it Firefox updated without my approval but it still shows the last update as 11/15/17.) After it completed the sync I opened Thunderbird again and found the last 5 days of emails were not in my inbox and Thunderbird will not download them again. It is downloading new emails when i receive them but not the ones it downloaded just before the freeze. Thunderbird is set to leave messages on server for at most 15 days and until I delete them. My question is how do I get Thunderbird to download the last 5 days worth of emails again without affecting all my other emails and without duplicating emails that were previously downloaded?