I have 4 Forests doing FIM GALSYNC with each other successfully - AMERICAS, EUROPE, AFRICA, APAC. But I don't want FIM to provision APAC contacts to EUROPE the same way it is doing for AMERICAS & AFRICA. When the APAC contacts are synched in EUROPE MA the targetAddress attribute value of the contacts should be SMTP:%mailNickName@myexch2010.apac.org but for all other forests APAC can provision the contacts with the targetAddress value in the format SMTP:%mailNickName@myexchdomain.com. Let me know how this is

Basically that would mean you need to change the GAL Sync code. The source code is available when you install FIM