Error Authenticating Proxy Account when Executing SSIS job I have a SQL Server instance that runs 5 scheduled tasks each night, each of which run SSIS packages.

These packages have been running for years and the associated steps run via a Proxy Account (PackageExecutor).  PackageExecuter is associated with a SQL Credential that was a former  domain admin account.

Soon, the domain associated with this admin account is going to be shutdown.   I have to use a new account, on a new domain, as the admin account associated with my roxy, PackageExecutor.  When I created a new Credential for the new Admin account and associated it with PackageExecutor, I started to get the following error when I tried to run one of my SQL jobs as a test:

Unable to start execution of step 1 (reason: Error authenticating
proxy *Domain\Admin_Account*@*fully.qualified.domain.com*, system
error: Logon failure: unknown user name or bad password.).  The step
failed.


If I'm understanding this reasonably explicit error, what it's telling me is that the Credential accounts, associated with my proxy is in correct.  How do I validate this?

I know that this account is legitimate-- I've already associated it with every associated server group, I've made it a sysadmin user on the server.

What could be causing this problem?

To be clear, I haven't mis-typed the account name or the password associated with the Proxy Credential.  However, when I entered the account name Domain\Admin_Account and clicked the Check Names button, SQL Server automatically transformed the User ID to the fully-qualified version.  I'm not sure if this has anything to do with this problem.

I'm at a bit of a loss.  I've given my credential account full access to everything that I can think of.  What might I need to do to get this to work?

UPDATE

Sorry, one more quick mention.  I've found this MSDN kb article.  Resolution method #1 is what I've been doing for years.  The others don't seem to apply, or I'm missing something.  Any tips or clarification would be beneficial.
Just in case others have gotten here for the same reason.  Make sure that the account your proxy/credential is using is a user in its default database in SQL Security.

We went through all the other suggestions (checking that the password hasn't changed, switching to a local service acct for SQL Agent User, rebuilding the credentials and proxy, etc.) and until we made sure the account was a user in its default DB, for some reason, that was causing it to pass a Null SID when it was trying to authenticate to AD.