About 2 days ago, all the message header buttons (Reply, Forward, Delete, etc) disappeared on just one of my Thunderbird accounts' Inbox. That account connects to a Microsoft Exchange Server email system via Exquilla. All of my other email accounts are "standard" (not using Exquilla add-on) and all of my other account Inboxes show the message header buttons when I click on a message header to see the full message in the lower message pane. Until about 2 days ago, all message header buttons appeared previously in all of my accounts (Exquilla-related or not). Since Exquilla was last updated more than 2 months ago, I tend to think that use of the Exquilla add-on is not the cause of this problem, but I include this info here to be as completely descriptive as possible. I am running Thunderbird 115.5.2 (64-bit), which Thunderbird "Help" informs me is "up to date".