Yes, it will help you recover the emails. The .dbt file is a temporary copy of dbx file. If any unknow system shut off or if outlook express crashed or there is not enough space in the hard disk and you cannot find your dbx file, there are chances you can get your messages from a file with extension .dbt.
Just change the extension of the file to .dbx (e.g. Inbox.dbt to Inbox.dbx) and open the renamed file in Remo Recover Outlook Express (.dbx) software to recover the emails.