Why can I not add a check constraint that makes the user enter an email ending in a specific address

Implementing: An employee email address should use the company domain. That is, the
email address should end with ‘abcco.com’.

alter table employee
add constraint emp_email_check check (co_email in ('%abcco.com'));

but I get this error

ORA-02293: cannot validate (ITAM.EMP_EMAIL_CHECK) - check constraint violated
02293. 00000 - "cannot validate (%s.%s) - check constraint violated"
*Cause:    an alter table operation tried to validate a check constraint to
           populated table that had nocomplying values.
*Action:   Obvious

>Solution :

The IN() predicate tests for exact string matches only. It does not support wildcards.

You should use

check (co_email like '%abcco.com')

Or alternatively:

check (left(co_email, 9) = 'abcco.com')