sendmail allow relaying based on recipient address

I am trying to set up a sendmail server in a development/testing environment, I want to allow relaying through this mail server to a specific list external email addresses, in order to test email notification in the applications being tested.  The test email accounts exist on multiple external email domains (our corporate domain, customer domains, gmail, yahoo, and hotmail).  While the contact information in the different application databases is suppose to be scrubbed for testing, mistakes have happened in the past that caused applications being to tested to send emails to regular customer contact email addresses, hence my desire to restrict relayed outbound email to a specific list of addresses.

My understanding is that the use of the "To:" tag in the access map, is supposed to be able to accept a full email address if the "Feature(blacklist_recipients) is used.

Currently I am able to use the "To" tag to allow relaying to specific recipient domains, but not to specific recipient addresses.

For example:
### start acccess file
To:companyname.com   RELAY
To:gmail.com     RELAY
To:yahoo.com   RELAY
### end access file

The above "works" in that it allows relaying to addresses like test@companyname.com and test@gmail.com, and doesn't allow relaying addresses of other domains like nontest@othercompany.com, unfortunately it still allows relaying to addresses like nontest@comanyname.com and nontest@gmail.com.

When I try:
### start access file
To:test@companyname.com   RELAY
To:test@gmail.com    RELAY
To:test@yahoo.com  RELAY
### end access file

It doesn't work, it doesn't allow relaying of mail to test@companyname.com.

Is there any way to get this to work?  or an alternate way to allow relaying to specific addresses, external to the mail server?

Thanks,
Jeff