I'm having an issue where Thunderbird stops getting emails every x minutes as it should, and when I trigger the retrieval manually, I get an error that states: The POP3 mail server does not support UIDL or XTND XLST, which are required to implement the "Leave on Server", Maximum Message Size", or "Fetch Headers Only" options. To download your mail, turn off these options in the Server Settings for your mail server in the Account Settings window. If I close and reopen Thunderbird, it starts working again (with no changes to the account settings) for a few hours, then the issue comes back. There's been no changes to my account settings either from my ISP or in my Thunderbird setup. In the past, I've seen this error very sporadically, but now it's happening at least twice a day. Thank you for your help... EB