B2C Store Creation Buyer Email error

When creating a buyer user email from current os's user name and adding buyer email from command, the replace function only replaces the first instance only and not all of them.
So when
Os's username is: abc@xyz.com
and buyer user email from command is: buyyer@gmail.com

the final email becomes abcATxyz.com+buyyer@gmail.com@salesforce.com

and gives the error that invalid email address