A problem with people not getting my messages has been plaguing me for a while and I think I've discovered the reason. When I reply to a message I notice the resulting window does not have the account (yes I'm using multi-account) drop down like new messages do. If I go back to the main ZD window and switch accounts before sending the reply, the message is sent under the account currently being viewed in the ZD window instead of the account of the original message.
This produces an immediate error from the server:
on the active account.Subject: Delivery failed: invalid request: invalid long value '863cbd4d-c2d4-4913-8fa6-c2874da9119c:4847' for attribute: origid