I have found that some of these low-frequency error messages Last error: 551 we do not relay for hi-volume lists are a result of email addresses RFC821 RCPT TO:<> that happen to use the lower-preference (higher number) MX RR when that email address has multiple MX hosts. Sometimes things are further obfuscated when that email address also refers to a CNAME record. This seems to "confuse" SENDMAIL anit-relay configs. Thus, when a VM/CMS SMTP client is involved, SMTP re-writes the RCPT TO: address to the CNAME address, and the secondard SENDMAIL gets the delivery, the above error occurs. Or so it seems to be from a recent PSID effort. /Pete