WowAce

Unfortunately, the newest patch broke the addon. It was working perfectly until Blizzard dropped the patch. 

1x ...ceBulkMail2\Libs\LibQTip-1.0\LibQTip-1.0-48.lua:543: attempt to call method 'GetBackdrop' (a nil value)
[string "@BulkMail2\Libs\LibQTip-1.0\LibQTip-1.0-48.lua"]:543: in function <...ceBulkMail2\Libs\LibQTip-1.0\LibQTip-1.0.lua:539>
[string "@BulkMail2\Libs\LibQTip-1.0\LibQTip-1.0-48.lua"]:132: in function `Acquire'
[string "@BulkMail2Inbox\BulkMailInbox.lua"]:956: in function `ShowInboxGUI'
[string "@BulkMail2Inbox\BulkMailInbox.lua"]:342: in function `?'
[string "@Ace3\CallbackHandler-1.0\CallbackHandler-1.0-7.lua"]:119: in function <...Ons\Ace3\CallbackHandler-1.0\CallbackHandler-1.0.lua:119>
[string "=[C]"]: ?
[string "@Ace3\CallbackHandler-1.0\CallbackHandler-1.0-7.lua"]:29: in function <...Ons\Ace3\CallbackHandler-1.0\CallbackHandler-1.0.lua:25>
[string "@Ace3\CallbackHandler-1.0\CallbackHandler-1.0-7.lua"]:64: in function `Fire'
[string "@Ace3\AceEvent-3.0\AceEvent-3.0-4.lua"]:120: in function <Ace3\AceEvent-3.0\AceEvent-3.0.lua:119>
[string "=[C]"]: in function `TurnOrActionStop'
[string "TURNORACTION"]:4: in function <[string "TURNORACTION"]:1>

Same, looks like LipQTip needs an update.  Until then you can manually update the Lib.  

Modify the LipQTip-1.0.lua file in the Lib directory

Change line 390 from

        tooltip = CreateFrame("Frame", nil, UIParent)

to

        tooltip = CreateFrame("Frame", nil, UIParent, "TooltipBackdropTemplate")

delete/comment out all these lines 544 to 551:

        local backdrop = GameTooltip:GetBackdrop()

        tooltip:SetBackdrop(backdrop)

        if backdrop then
                tooltip:SetBackdropColor(GameTooltip:GetBackdropColor())
                tooltip:SetBackdropBorderColor(GameTooltip:GetBackdropBorderColor())
        end

 Credit to xodiv for the solution.