Hi,
The Outbox contains the messages that are yet to be sent. As soon as a message is sent, it is moved to the "Sent from device" folder.
As for the red exclamation mark, I don't know how to diagnose such problems with a SMTP server. Maildroid does not have logs I don't know why. :(
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Andrew K. Lovetski
Sent from my Android 2.1 update1 Samsung i9000 GalaxyS device by Maildroid 1.92, IMAP to Exchange 2007 sp1
Thanks the developer is helping us.