Secure Mail certificates are associated with a specific email address. This means that you cannot change your email address without first disabling Secure Mail for your mailbox.
Note:Once you deactivate Secure Mail, you will ONLY be able to decrypt and view previously encrypted messages on your current computer. You will need to export your certificate in order to decrypt messages on another computer. You may export your Secure ID from Tools & Settings > ID & Password Tools > Backup / Export Secure ID > type in your Secure ID password and specify location and file name.
Following are some possible solutions, depending on the reason for changing your primary email.
To use two email addresses to send and receive secure mail:
Create one mailbox for each address. Open both in Outlook, and activate Secure Mail for both.
To change or remove your primary domain name:
Unfortunately, you will need to deactivate Secure Mail. Change your primary domain. Then activate Secure Mail to obtain certificates for the new domain.