[Zope] leave the plone site under a domain to access a php webmail

Hi I have a question about my new plone site. How I can configure apache or zope to access to my old webmail (php aplication) under my new plone domain. I using zope and plone with apache server (with ProxyPass option) My new site is http://www.gualeguaychu.gov.ar I want to access to my old website under http://www.gualeguaychu.gov.ar/mail, but it would have to leave the plone site and access with apache to my old php webmail and this not works (I have the "404 Not Found" message). Excuse my poor english and thanls in advance. roberto