Notrihills,
Please read you own original post thoroughly. It clearly indicates that you have a "
hidden read receipt." Now, that hidden receipt is trying to send on every launch of your outgoing email and it is failing as described in the Microsoft bulletin. The fix is also described in the Microsoft bulletin as well. However, if you are not looking to fix this problem permanently, you can try this stop-gap measure to delete that hidden receipt (which keeps trying to resend) and that should free-up your outgoing mail connection (until you get the next request for a read receipt):
Delete Read Receipts using OutlookSpy