I don't quite understand this.
Do you mean it may be stuck on your mail server but you can't download it to your mail clients? I've seen that happen but rarely. Is this under POP3? If so, you could use raw POP3 via Telnet to inspect the server mailbox.
Also the Lock Screen constantly shows 1 email unread but I can find it. Anyone know how to clear this?
Is that like Windows' System Tray? On a Win PC that will appear in the Registry like:
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\UnreadMail\Your eMail Addy@Domain]
1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 20 Meg WBC