If your primary email address changes, or you want to change the email address associated with your account, you may do this from PoliteMail > Account Settings > Users & Groups.
Please note, the email address you change to MUST be a valid email address you can recieve email to. In other words, if you want to send from another email address (e.g. email@example.com) besides your personal address, just changing the address within PoliteMail WILL NOT produce the result you want. Instead, your email administrator must create that additional address within your Outlook account (so you can send/receive email to/from that address), then you will be able to send from that address in both Outlook and PoliteMail.
From PoliteMail > Account Settings > Users & Groups
Double-click on your User Name
Edit your Name and/or Email address within the dialog, then click Save
(if you are running PoliteMail on the same machine, it is not necessary to change your registration key)
Now restart Outlook, and from PoliteMail > Connections Setting, input the new email address