Recently my wife received an Email addressed from jdavidson4 at home.com. When she tried to reply to the original message her reply bounced with ----- The following addresses had permanent fatal errors ----- <jdavidson4 at home.com> (reason: 553 5.3.5 system config error) ----- Transcript of session follows ----- 553 5.3.5 home.com.nurdog.com. config error: mail loops back to me (MX problem?) 554 5.3.5 Local configuration error I started to do some digging and discovered that there is no MX record for home.com which is the ultimate reason my wife's message bounces. However what disturbs me is that given the lack of DNS MX record for home.com my Email server is tacking my domain name nurdog.com onto the original domain name and creating home.com.nurdog.com. I verified that this action is indeed occurring: # sendmail -bt -C./sendmail.cf ADDRESS TEST MODE (ruleset 3 NOT automatically invoked) Enter <ruleset> <address> > 3,0 jdavidson4 at home.com canonify input: jdavidson4 @ home . com Canonify2 input: jdavidson4 < @ home . com > Canonify2 returns: jdavidson4 < @ home . com . nurdog . com . > canonify returns: jdavidson4 < @ home . com . nurdog . com . > parse input: jdavidson4 < @ home . com . nurdog . com . > Parse0 input: jdavidson4 < @ home . com . nurdog . com . > Parse0 returns: jdavidson4 < @ home . com . nurdog . com . > ParseLocal input: jdavidson4 < @ home . com . nurdog . com . > ParseLocal returns: jdavidson4 < @ home . com . nurdog . com . > Parse1 input: jdavidson4 < @ home . com . nurdog . com . > Mailertable input: < home . com . nurdog . com > jdavidson4 < @ home . com . nurdog . com . > Mailertable input: home . < com . nurdog . com > jdavidson4 < @ home . com . nurdog . com . > Mailertable input: home . com . < nurdog . com > jdavidson4 < @ home . com . nurdog . com . > Mailertable input: home . com . nurdog . < com > jdavidson4 < @ home . com . nurdog . com . > Mailertable returns: jdavidson4 < @ home . com . nurdog . com . > Mailertable returns: jdavidson4 < @ home . com . nurdog . com . > Mailertable returns: jdavidson4 < @ home . com . nurdog . com . > Mailertable returns: jdavidson4 < @ home . com . nurdog . com . > MailerToTriple input: < > jdavidson4 < @ home . com . nurdog . com . > MailerToTriple returns: jdavidson4 < @ home . com . nurdog . com . > Parse1 returns: $# esmtp $@ home . com . nurdog . com . $: jdavidson4 < @ home . com . nurdog . com . > parse returns: $# esmtp $@ home . com . nurdog . com . $: jdavidson4 < @ home . com . nurdog . com . > I run a second server that does not have this problem and this issue only seems to occur on domains with broken DNS. For example if I use an email address which comes with a working server I get: > 3,0 prg at cirrus.com canonify input: prg @ cirrus . com Canonify2 input: prg < @ cirrus . com > Canonify2 returns: prg < @ cirrus . com . > canonify returns: prg < @ cirrus . com . > parse input: prg < @ cirrus . com . > Parse0 input: prg < @ cirrus . com . > Parse0 returns: prg < @ cirrus . com . > ParseLocal input: prg < @ cirrus . com . > ParseLocal returns: prg < @ cirrus . com . > Parse1 input: prg < @ cirrus . com . > Mailertable input: < cirrus . com > prg < @ cirrus . com . > Mailertable input: cirrus . < com > prg < @ cirrus . com . > Mailertable returns: prg < @ cirrus . com . > Mailertable returns: prg < @ cirrus . com . > MailerToTriple input: < > prg < @ cirrus . com . > MailerToTriple returns: prg < @ cirrus . com . > Parse1 returns: $# esmtp $@ cirrus . com . $: prg < @ cirrus . com . > parse returns: $# esmtp $@ cirrus . com . $: prg < @ cirrus . com . > This obvious thing to try was to remove FEATURE(always_add_domain), run m4 and restart sendmail but that had no effect. I am not that concerned about this problem, but for the life of me googling and comparing the config files between my two Email servers does not indicate anthing obvious to me to cause this behavior. Does anyone have an idea to which sendmail config parameter might be causing nurdog.com to get tacked onto home.com in these circumstances? Thanks for any ideas. -- Paul (ganci at nurdog.com)