Maybe it's a bug, but if not, I would like to put this on the wishlist:
Instead of showing a summary of my unread mail in my inbox (eg. like Thunderbird does: "Inbox" and then a number), Unity Mail displays every single one of my unread mails in the Messaging Menu. I tend to get a lot of mail, so this quickly blows up my Messaging Menu (esp. on a netbook), where each additional line in the menu makes it more and more overcharged. Due to also having Empathy and Thunderbird in the Menu, after about 5 unread mails the Messaging Menu is too large for the screen and I have to scroll down.
So, if this is not a bug and is indeed by design, I would like an option to only display the summarized unread message count in the Messaging Menu (like it already does on the Launcher icon), and/or maybe show only the most recent unread mails in the menu.
I'm running Quantal Beta 1 with the latest unity-mail package from the quantal repositories.
I don't see any point in displaying the "summary" as the Launcher item already does that. Will "display only last 10 messages" option suit you?