Whenever I close eM client it tells me there is 1 unsent item in Outbox

I get this message every time I close.  I can eliminate message by telling it not to appear, but why does eM client believe my empty Outbox has a message?

Hi Richard,
are all your outboxes truly empty? Have you checked in the Smart folder outbox?
Otherwise I’ll need to know more about your situation, what mail provider and mail service are you using on your accounts, what version of eM Client are you running?
If you want to just avoid this pop up you can uncheck the option “Don’t close application until all messages are sent” in Tools > Settings > Mail > Send.

Best regards,