SQL Server login failed due to "The password of the account must be changed"

After deploying an ASP.NET application to the production server, I encoutnered this error: Login failed for user 'db_user'. Reason: The password of the account must be changed. The application is using SQL user authentication to logon to SQL server. Therefore, a close inspection on the user account is warranted. It appears that the application user account has set the Enforce password policy, Enforce password expiration and User must change password at next login were turned on. Therefore the password must be modified before the application could access the database. I've got hold of the the DBA login to logon to the database server, and try to remove the checks mentioned above on the application user account, but an error says MUST_CHANGE constraint, and the checks cannot be removed. Therefore, I login into the SQL Server again using the application user account in question, and then I get a prompt to modify the password. Once the password is changed, the checks can be removed, and I change the password back to the previous password that was meant to be used for production. That seems to solve the problem as the application is able to load the data drom DB without error.