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Is it possible that they have a load balancing device between 2 mail servers, but only the higher priority one of the two has forwarding routes setup? Alternately, what do your mx records look like, can you post them? What do the A records the corrolate to the MX records look like.. Is it possible there is more then one A record for the same name pointing to different IP addresses? (This might cause a round robin effect, IE, if mail.yourdomain.com has 2 A records, 1 for xxx.xxx.xxx.xxx and one for yyy.yyy.yyy.yyy, with xxx being your mail ip, yyy being backup mail ip) This may make hosts sending mail alternate between which mail server they send mail to, when the backup goes offline, they are getting some other server or soemthing crazy like that. Just a couple ideas.. Jim Barstow Internet Network Engineer Local Internet Services, Inc. PO Box 160 Ludington, MI 49431 (231)845-9797 ext. 109 -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of Bill Rakowitz Sent: Thursday, July 25, 2002 6:21 PM To: [EMAIL PROTECTED] Subject: [VOPmail Beta] delivery failures * This is the vopmailbeta mailing list * We've run across something strange. We're running ModusMail 1.4 We run DNS in our network and assigned our mail server a priority of 10 We use our backbone provider as secondary DNS *AND* secondary mail server (smart host?). We have the smart host entered into our DNS with a priority of 20. The backbone provider's DNS (secondary) matches the above. We began getting contacts from people (non-customers) indicating that when they attempted to send a message to our domains, they would get a "user unknown error". We verified the ModusMail server was alive and the account was ok. We also found that only specific systems were not able to deliver these messages to our domain while other systems continued to deliver messages to the same accounts with no problem. Ultimately, we learned that the back up email server had gone off-line and removing the back-up mail server from our DNS made the problem go away. The back-up mail server was repaired, returned to service and we added it back into DNS. Everything runs well for about a week. Today, I start getting contacts that external users are again getting error messages, but this time they are "mailbox unavailable (SMTP Error Code 550)". Guess what - the back-up mail server had died again. Removing it from DNS corrected the problem. Why would a failure of a backup mail server that is listed in both DNS with a higher priority than the primary email server cause a "user unknown / mailbox unavailable error"? I can't understand why a failure in a back-up server would be service effecting ??? Bill Rakowitz YK Communications ** To leave this list, send an email to [EMAIL PROTECTED] and put the word "LEAVE" in the BODY of the email. ** To leave this list, send an email to [EMAIL PROTECTED] and put the word "LEAVE" in the BODY of the email.
