Based on your query, one way is to contact the employer and ask them to enable the email for a smaller period and then contact Microsoft support to change the email. Refer: https://trainingsupport.microsoft.com/en-us/mcp/forum/all/change-email-address-associated-with-mcp/89c89ee6-cbff-4ede-8864-dbdb7bc5fb3e
If that option is not possible, try contacting training support. Microsoft Certification Program have its own support channel and is not supported in Q & A. Find the training support website belo.
https://trainingsupport.microsoft.com/en-us/
The training support website contains several threads, where you can post your query and get the response.
https://trainingsupport.microsoft.com/en-us/mcp/forum
Hope this helps