I setup a small box with Server 2003 64bit to be used as a webserver and email server for a small school. Real simple stuff for a few users. A simple website and a handful of emails. rDNS and spf records setup and pass every test I found including test at dnsstuff.com.
Email sending to almost every email address (google, hotmail, aol, whatever) works. However, with one domain, I get an bounce back with the error.
550 Requested action not taken: mailbox unavailable
It's another school running Exchange judging from some packet sniffing with WireShark. Every email on this domain I have tried sending to gives this error. The email address is valid as I can send to it from my personal, and gmail account without a problem.
Does anyone know of some anti-spam software that gives an 550 error like the above? What else could this be?
Thanks for any suggestions.
Packet capture of the two servers communicating look like this.
220 <server snip> Microsoft ESMTP MAIL Service, Version: 6.0.3790.3959 ready at Sat, 2 Oct 2010 12:48:17 -0700 EHLO <email snip> 250-<server snip> Hello [<ip snip>] 250-TURN 250-SIZE 250-ETRN 250-XXXXXXXXXX 250-DSN 250-ENHANCEDSTATUSCODES 250-8bitmime 250-BINARYMIME 250-XXXXXXXX 250-VRFY 250-X-EXPS GSSAPI NTLM LOGIN 250-X-EXPS=LOGIN 250-AUTH GSSAPI NTLM LOGIN 250-AUTH=LOGIN 250-X-LINK2STATE 250-XXXXXXX 250 OK MAIL FROM: <email snip> 250 2.1.0 <email snip>....Sender OK RCPT TO:<email snip> 250 2.1.5 <email snip> DATA 354 Start mail input; end with <CRLF>.<CRLF> <email body here> . 550 Requested action not taken: mailbox unavailable QUIT 221 Goodbye