Gmail – Is it possible to get the total unread mail count with Priority Inbox

If someone sent me mail from a client/application that sends the urgent flag, will this automatically be sent to important messages section ?

Maybe, maybe not. It was not stated in the Gmail Help. It seems like Gmail will do it automatically based on user action (your action). Reference: How Priority Inbox works

If not, is there a filter I can apply to get it to do this ?

You can create filters as usual (based on sender, subject etc) and mark the emails as important.

Yes you can do this but not without a little bit of hacking around.

From my answer at Equivalent of 'archive' for priority inbox \ multiple inbox :

The only way that I have found to do it is either with the element inspector in chrome/safari or with firebug in firefox. The good news is that once you have made the settings change it will work in all browsers.

1. Go to the priority inbox settings tab.
2. Click the options next to the section you want to show your work mail.
3. Click "More Options..."
4. Inspect the element for the "Work" Label
5. You will notice on the surrounding div there is an attribute cfg="^all,Work", change the value to "^i,Work"
6. Select the label on the page as you normally would

You will know if it worked or not straight away because the section settings should now read : Inbox, Work instead of the All Work that it used to read.

Here is a list of alternative commands you can use. You can chain commands together with a comma.

^i = Inbox
^u = Unread
^io_im = Important
^t = starred
^f = sent
^r = drafts
^all = All mail (include archive)

ie. ^i,^u,Work = all emails in your inbox, that are unread with the label "Work".