Setting the Pool in STREAM_MATCHED

I wonder if you are making things harder that it should be. Sounds like you already have the stream filter configured to map the internal uri (mail server addresses) to the VIP.

 

 

If you enable cookie persistence, BigIP will do the heavy lifting of ensuring that the clients are directed to the node it connected to originally (nodes with the notes login). If cookie persistence does not work for some reason, you can always hand roll the persistence entries you self (as a bonus you could delete the persist entry when the user logsoff). There should be plenty of examples to show you how to do this.