WithEvents object in Outlook VBA eventually fails to raise event - vba

Question

Okay, looks like someone has encountered this problem before, but I didn't see any further comments or solutions. See the Edit in the accepted answer to this question.
My situation is like this.
I am running Outlook 2013 under Win10 x64 with an Exchange email account. I sometimes run Outlook for several days to a week or more at a time without closing it.
I want to raise an event when a new item is added to the Sent Mail folder. This needs to occur after the Application ItemSend event because, let's say, I want to delete the message after it is sent, which you cannot do from within the ItemSend event handler.
So I have the following code:
Public WithEvents goSent As Outlook.Items
Private Sub Application_Startup()
'Establish the global object for the folder we want to monitor.
Set goSent = Session.GetDefaultFolder(olFolderSentMail).Items
End Sub
Private Sub goSent_ItemAdd(ByVal Item As Object)
'Do stuff here.
End Sub
Everything works beautifully for a day or longer, but eventually the ItemAdd event handler stops firing. If I enter the VBA editor and manually run Application_Startup, then it starts working again.
[Edit:] One other bit of information: The "built-in" events, like Application ItemSend, always seem to fire reliably no matter how long Outlook has been running.
[Edit 2:] This time, I let things go for a day after the event stopped firing. I opened the VBA editor and put a breakpoint in the Application ItemSend procedure. When it stopped, I queried the goSent object and found that (a) it still existed (rather than being Nothing), but (b) it had only the items in it that were there yesterday, presumably at the time it became "untethered" from the Sent Mail items collection. When I submitted a new Set statement in the Immediate window, it immediately began to work again.
[Edit 3:] I noticed that the MSDN documentation says to put event handlers for custom objects--like my ItemAdd event--in class modules. I have mine in ThisOutlookSession, but it was my understanding that ThisOutlookSession is a class module. Is there a problem with that?
Any idea why this would happen and what to do about it? I considered adding an event handler for Application ItemSend and just reassigning the goSent object every time that's fired, but it doesn't address the underlying problem.
[Edit 4:] For a while now, I've had a Set statement in the Application ItemSend handler, and that seems to have mostly taken care of things, even though it's a workaround, not really a solution. It appears to fail when I have delayed delivery on a sent item for an extended time, and I don't send any further messages in the meantime. Then the goSent object disconnects from the Sent Mail collection, and the message is actually sent from the Outbox after that point and before Application ItemSend fires again.
Thanks!
[Edit 5:] Unrelated to original issue: I discovered that my macros fail to accomplish what I want with an Exchange server that is in online mode (i.e., not cached mode) if I have messages in the Outbox with delayed delivery and Outlook is closed when the delivery time passes. In online mode, Exchange itself sends these messages and adds them to the Sent Mail folder on the server, so when Outlook reopens, the messages are already in the Sent Mail collection and no event fires. Which makes sense. See discussion here. Looks like I would need to add something to my Application_Startup macro to look for messages sent since Outlook last closed.

Answer 1

I had similar issue and never found a proper solution. What I did was I wrote a little batch script that closes and opens outlook app, then I set a task in task scheduler to run it every hour outside of my working hours. You can also do it easily in vbs.