I'm using thunderbird 115.10.1 on Ubuntu Linux. I've set up a second calendar and associated it with an email account hosted by Polaris Mail. That email address has worked fine within thunderbird for everything else for a long time, but I only recently associated it with a calendar. When I get a meeting invite, for example from a gmail user, and accept that invite, selecting "send a response now", no message ever arrives at the email of the inviter and no email ends up in any of my folders (drafts or sent). It is like nothing happens. The event *is* accepted and added to the calendar, but no respose is created or sent. I have another email account and calendar and meeting acceptances and responses seem to work fine. I've looked at all the settings I can find and they seem appropriate and analogous to those with the working email/calendar. The correct email address appears in the calendar properties opened by right-clicking on the Calendar and selecting properties. Any help? Thanks.