Moving messages from one mailbox to another

Hi all,

I've got a user that recently retired after 25 years here.  There are messages in this mailbox that I would like to move to the mailbox of the person taking on that role, and I am looking for guidance on the best way to accomplish this.  I could do this using the Outlook client, but there must be a better way.

I know I could convert the user's mailbox to a shared mailbox, but I'd like to do away with the email address as it is primarily sales emails coming in now. 

Thanks

Steve