I use Versamail on my vzw Treo 650.
I set up a gmail account to have work emails forwarded into.
In Versamail's preferences/reply options, I put in my work email address in the "reply to address with" so that the email I send appears to be coming from my work address and when the respondent hits 'reply' the email will be directed to my work email addresses.

But no dice.

When the respondent hits 'reply' it goes to the gmail address the versamail is pointed to.