Bruce, Hmm, brmiller.ca does not have an A address. The MX addresses associated with it are: brmiller.ca. 7200 IN MX 0 mail5.zoneedit.com. brmiller.ca. 7200 IN MX 0 mail6.zoneedit.com. mail5 and mail6 are: mail5.zoneedit.com. 7200 IN A 69.64.89.63 mail6.zoneedit.com. 7200 IN A 66.240.226.247 so mail5 is the MTA that objected. Also, it's highly likely that you're using a mail service rather than running your own MTA. You can try to talk to it yourself - SMTP is a plaintext protocol - check out http://www.linuxjournal.com/content/sending-email-netcat http://www.georgetoft.com/?QMail:Testing_Mail_Servers:SMTP_Testing_(Using_Telnet) Try it out with netcat or telnet (on mail5 and mail6) and see if it refuses to relay mail for you. If so, you have some solid data for your provider. If not, ... well I dunno. It behaves differently in different cases. I see you have sent another email to the oclug-tech list to say the provider claims the problem is fixed. With this technique, you can check each MTA individually right away and get back to them right away, instead of waiting for more mail to bounce/go missing. Bill Strosberg had excellent advice as well - including re: DNS reverse pointers. Although it looks like the reverse pointers are fine for mail5 and mail6. bjb