iPhone ActiveSync showing sent email in Inbox

Curious if anyone else is experiencing ActiveSync email accounts showing sent email in your iPhone mail.app Inbox.

Messages still appear even if "organize by thread" is disabled.

iPhone mail seems to handle native Gmail accounts correctly, knowing to hide any sent email, however my Google Apps ActiveSync account/mailbox doesn't.

Is this a known limitation? I've deleted and re-added my ActiveSync account and it still occurs.

No - this is not normal and I haven't heard of any fix short of deleting the account and trying again. If the store on the phone gets really corrupted, you may have to restore and set up the phone as new - but do try lesser steps first.