Thunderbird ver 45.0 & Lightning ver 4.7 WebDAV sync to calendar on my acct. at www.mail.com An Event popup reminder presents. I click "Dismiss." It immediately results in the dialog box "This item has recently been changed on the server. Submitting your changes will overwrite the changes made on the server: <submit changes anyway> <discard my change/reload> Regardless which I select, the "...changed on the server..." box immediately reappears. First: What is the implication of the message in that dialog box? It means nothing to me. Furthermore, it doesn't seem to matter which button I select; the dialog box immediately reappears. The only way I've found to dismiss the original event pop-up reminder is to edit the event to delete it. I wish there were documentation explaining that "...message has changed on the server..." dialog box. I don't understand what action I ought to take when it presents. --Especially since neither button selection seems to do anything other than recycle that dialog box. The only way I have found to stop the appearance of the dialog box is to go to the calendar Event, and delete it.