Hi, Following a several discussions on devel + users and sip-implementers mailing lists, I just added a new module parameter in TM to control how the 6xx replies are handled: -(0) the 6xx replies will block any further serial forking (adding new branches). This is the RFC3261 behaviour. -(1) the 6xx replies will be handled as any other negative reply - serial forking will be allowed. Logically, you need to break RFC3261 if you want to do redirects to announcement and voicemail services. Again, this is more a logical debate (about the 6xx replies).See: https://lists.cs.columbia.edu/pipermail/sip-implementors/2008-June/019413.h… and this new param was added to let you choose between: - following RFC, but not being able to implement some scenarios - breaking RFC, but being more practical ;) Best regards, Bogdan