Did several users have this issue or just only the current user?
Whether the Outlook 2007 was connected via POP3 or IMAP?
If it is MAPI client, please use MFCMAPI tool to verify the email is deleted indeed.
1, Download MFCMAPI using the following link:
2, Launch MFCMAPI tool on the user’s client.
3, Go to Session -> Logon and Display Store Table
4, Select the outlook profile of the user and double-click “Mailbox - your user name”
5, Expand "Root Container"
6, Expand "Top of Information Store"
Note: if the user has configured the outlook profile to use cached mode, we need to expand “IPM_subtree” under root container
7, Select on "Inbox", double click to open it
8, Find the messages, if stay there, please right click it and delete it.
9, Then please select “permanent deletion (deletes to deleted item retention if supported)” and click OK.
10, Close MFCMAPI dialog boxes, and click Session -> Logoff in the MFCMAPI main window. Close MFCMAPI main window.