How do I replace a substring of a string before a specific character?

Question

Table Email:

Values:

josh@yahoo.com
carmine32@hotmail.com
zehmaneh@yahoo.com

I want to replace the string before

Answer 1

declare @t table(email varchar(30))
insert @t values('josh@yahoo.com'),
                ('carmine32@hotmail.com'),
                ('zehmaneh@yahoo.com') 

select stuff(email, 1, charindex('@', email), 'Test@') 
from @t

Result:

Test@yahoo.com
Test@hotmail.com
Test@yahoo.com