Open Wife identity and create a new Folder called 'Wife emails' (without the ' ')
Drag all the emails (both received and sent emails) that you want to save into the new Wife emails folder.
Change to Husband identity
File > Import > messages >
In Select Program choose Microsoft Outlook Express 6 > click on Next
In Import from an OE6 Identity choose Wife identity > click on OK
In Location of Messages (it will have found the store folder and that bit will be filled in) > click on Next
In Select Folders put the green dot in Selected folders and select 'Wife emails' folder > click on Next
In Import Complete (feel smug) and click on Finish
Note: You need to rename the folders in your wife's identity as you cannot import one with the same name as in Husband's identity. You also cannot rename the Inbox, Outbox, Sent Items, as they are system folders. You need to move the emails to another folder that you have made.