Problem changing primary email address

Problem changing primary email address

The email address I used when setting up my (free) Zoho account years ago no longer exists.  This useless email address exists is my primary email address in the Contact Details of my Zoho profile.  When I try updating the information with a current existing email address I get a message "Email ID already exists".  This is perhaps because I recently set up a Zoho account for a non-profit organization using that email address.  Unfortunately, that is the only non-Zoho email address I have.  I tried specifying that other Zoho address, but it was rejected, too.  Is there no way for my existing non-Zoho email address to the the primary contact email address for 2 Zoho accounts?