Hi all, I see a periodic problem with some email servers that report "User Unknown" for valid users. The most recognizable problematic host is hotmail.com, but there usually are others mixed in (today's additional problematic hosts included msn.com, verizon.net, and incentre.net). Here is one of the errors: Dec 13 11:20:55 mail sm-msp-queue[5360]: iBDGFPc0004630: to=<frank-****@msn.com>, delay=00:05:30, xdelay=00:00:00, mailer=esmtp, pri=470333, relay=mx1.hotmail.com. [64.4.50.99], dsn=5.7.1, stat=User unknown I found this post on Neohapsis that suggests the problem is DNS/firewall related: http://archives.neohapsis.com/archives/postfix/2004-03/1774.html What I can't understand is why this would be periodic and what, if anything, I can do to validate the authenticity of the errors? Do others see this same issue? -Jim P.