Please let me know how can I change or delete the secondary mail id which is linked to admin account. 

This is my first time, when trying to setup mail setup created user itadmin@prachinbharat.com after completion of setup and getting verified with domain, it asked for preferred user name and I entered naveen. Now while creating naveen as user for this time it's not allowing. 

Kindly help me to solve this problem. 

Regards

Vasant B Alagundagi.

9900785307