Hi, I've been using Thunderbird for years. For the past couple of years, I've used it to send and receive my work email from an Outlook/Office 365 IMAP account. It's mostly worked fine. Then this morning (I'm pretty sure this was working fine Thursday or Friday last week) I noticed that new email was not coming into the Inbox. When I checked the Outlook 365 web UI, I could see new messages. I've discovered if I completely close Thunderbird and reopen, I can see the new messages, but only once. If I do a repair folder operation on the Inbox, the new messages also show up. But no combination of 'Get Messages' or any other normal activities (besides which the account used to show new emails almost immediately after they were sent due to the joys of IMAP, I think) seems to work. I have had and still have under 'Server Settings', 'Check for new messages at startup', 'Check for new messages every 5 minutes' and 'Allow immediate server notifications...' all checked. The other weird thing is that this appears to be a problem on both my work computer and my home PC, both running Thunderbird, both attached to this Outlook 365 account in the same ways. This of course makes me suspect it's a problem with Microsoft servers where something has changed recently, but I wanted to check in to see if this might be a new problem anyone has a workaround to or something that's been around for awhile that could be fixed by me. Thanks.