Hi list... We have several sites in our organization. One site runs Exchange 2000 native, one site (our backbone) is in mixed mode running one 5.5 and two 2000 (one OWA and one as backbone with connectors) and the other sites are all running 5.5 native. Mail flow within the Exchange 2000 sites are no problem, mail flow between the "old" exchange 5.5 organization also. The problem is that a mailbox created on the 2000 server in the backbone site is not able to send or receive mesages to or from most exchange 5.5 sites (well not all, one site receives and can send mails from the mailbox on the exchange 2000 server, this site has a X.400 connector and a site connector to the 5.5 in the backbone site). Event log writes 9318 with error code of 5 from the MSExchangeMTA service. I already studied http://www.eventid.net/display.asp?eventid=9318&source= and read through all Q articles mentioned there. Tried the following: 1. configured name resolution on the problematic 5.5 servers so they can find our exchange 2000 server 2. set up a RGC from the Exchange 2000 to the old 5.5 sites (although i thought they should communicate over the existing connectors of the 5.5 in the same site?!) But nothing works. Anybody has another solution? Greetings.. Knapp -- COMPUTERBILD 15/03: Premium-e-mail-Dienste im Test -------------------------------------------------- 1. GMX TopMail - Platz 1 und Testsieger! 2. GMX ProMail - Platz 2 und Preis-Qualitätssieger! 3. Arcor - 4. web.de - 5. T-Online - 6. freenet.de - 7. daybyday - 8. e-Post