I seem to be having an issue with the use of Persona's as well.
I using a Split domain. and have a setup like this:
user@comp1.com +
user@comp2.com
comp1.com is the primary account, comp2.com is setup as an alias for the user.
Then under the user I setup a persona that should take any email sent to comp2.com and forward or reply back using the info from comp2.com
Unfortunately everytime I test this, the mail shows it has been forwarded by the comp1.com primary account.
Is my concept wrong. Hopefully someone can point out where I am going astray <g>
Mark