NotifcationUtil.sendNotification and email FROM address?

Hello Experts-

This *seems* so simple, but I can't get it to work... I want to be able to change the "FROM" email address based on purpose of the explicit script job using one of the Custom Mail templates, so the responses can go back to the correct people who need to handle them.

What is the purpose of sender on this IAPI call?  I thought it would change the "FROM" in the email address, but it doesn't seem to do anything...  The email sender remains as the system-wide email address.

     sendNotification(

      java.lang.String[] recipients,

      IapiAccountIfc sender,

      MailTypeEnum notificationType,

      java.util.Properties notificationParameters,

      java.lang.String attachmentDisplayName,

      java.io.InputStream attachment)

Other things I've tried:

1)

I experimented with the System Properties messaging.mail_source_policy settings thinking maybe it had to be set to DEFER_TO_MAILTYPE.  That didn't seem to work.  Unless I'm overlooking it, I haven't been able to find any documentation on what this does specifically...

2)

It does use a different one, if I set messaging.mail_source_policy to SPECIAL_ADDRESS and supply the address in messaging.force_from_address, but this doesn't help me because it changes it for all jobs.  I've also tried the "REPLY TO" equivalent to this.

3)

I also have script that uses the Java class to send emails directly rather than through the sendNotification function.  This works, but I can't use predefined templates and it doesn't put any entries in the "Processed Messages" log.

If anyone has gotten this to work or can point out what I'm doing incorrectly, please let me know.

Thanks in advance,

Mike