E2K3 SP2 on W2K3 SP2. Mail sent to one company gets bounced back. NDR is "4.3.2 This message was rejected due to the current administrative policy by the destination server. Please retry at a later time. If that fails, contact your system administrator." This started happening about a month ago outof the blue. And while I've come across internet posts that 4.3.2can also meana temporary problem, at this point it is hardly temporary.I know the cause is not our Exchange setup. Aside from the obvious fact thatthe mail goes out and the error indicates the receiving end is cause, I manage our Exchange and I know all the settings. And, our servers are not on any blacklists (which is the first thing I checked). I don't think thereceiving company is the actual cause either. It isa small non-profit org I volunteer at. I don't manage their server but I know it is E2K3 on SBS,the IT person (also volunteer) did not set a policy just to reject mail from me, they receive allother outside mail,and I can send mail to them from my home email account. However, the non-profit uses a service-- it is not their ISP --toforward email thru. That service did not see any of my emails in their queue records when I called them to troubleshoot (e.g. as if the emails never reached their servers), but that is the only logical part of the chain to suspect.btw, the email messages contents would hardly be marked spam by any filter.Any thoughts, help much appreciated.Thanks,jremmc

As the NDR shows, it seems that messages was rejected by the remote server Please telnet to the problematic remote domain and check if you can send the messages? Please contact that service and check if their router is receiving any communication from your exchange server Resources: Cannot send or receive e-mail messages behind a Cisco PIX firewall

No luck. Sorry for replying week later; holidays shortened work time. Telnetting from my office to mail server did not get response (no welcome; timed out). A popular MX lookup Internet tool was able to test ok using its own info. PTR resolved to different host name than the mail server name sending the NDR. Anyway, not worth troubleshooting further for me. I'm only one affected (no one else from my company sends the org email) and I can use their personal email accounts to send to.Thanks,jremmc