"If mailgate1 is always available, will it be the only connector that takes the mail unless it has reached the maximum number of sessions ?"
Yes, although I have seen my 'secondary inbound' box accepting mail when the 'primary' box was clearly available. If you'd like them load balanced then have the preferencs set the same. "If mailgate1 is down, how quickly does the sending SMTP connector give up and try the next MX record pref, i.e immediately or after a certain retry parameter ?" Immediately as far as I understand it. If mail.wheaton.com is unavailable, it then tries mail1.wheaton.com, if that is unavailable, my ISP starts to queue the mail for me and will for the next 24 hours or until one of the MX records with a lower cost becomes available. I believe all of this is outlined in the RFCs. >From RFC 974: "If the list of MX RRs is not empty, the mailer should try to deliver the message to the MXs in order (lowest preference value tried first). The mailer is required to attempt delivery to the lowest valued MX. Implementors are encouraged to write mailers so that they try the MXs in order until one of the MXs accepts the message, or all the MXs have been tried. A somewhat less demanding system, in which a fixed number of MXs is tried, is also reasonable. Note that multiple MXs may have the same preference value. In this case, all MXs at with a given value must be tried before any of a higher value are tried. In addition, in the special case in which there are several MXs with the lowest preference value, all of them should be tried before a message is deemed undeliverable." Try. http://www.faqs.org/rfcs/rfc974.html Matt ----- Original Message ----- From: "Adam Romain" <[EMAIL PROTECTED]> To: "Exchange Discussions" <[EMAIL PROTECTED]> Sent: Tuesday, April 23, 2002 5:50 AM Subject: DNS behaviour with MX preferences... Guys, I'm trying to fully understand what happens with MX preferences and SMTP relays. Let me draw a picture. Lets says a company has 2 SMTP inbound connections for domain name example.com and the MX records show that example.com has 4 servers that will accept the mail. i.e. mailgate1.example.com pref = 10, mailgate2.example.com with pref = 20, fallback1.isp.com pref = 50 and fallback2.isp.com pref = 50. If mailgate1 is always available, will it be the only connector that takes the mail unless it has reached the maximum number of sessions ? If mailgate1 is down, how quickly does the sending SMTP connector give up and try the next MX record pref, i.e immediately or after a certain retry parameter ? TIA Adam Romain ********************************************************************** This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the system manager. Network Defence Ltd ********************************************************************** _________________________________________________________________ List posting FAQ: http://www.swinc.com/resource/exch_faq.htm Archives: http://www.swynk.com/sitesearch/search.asp To unsubscribe: mailto:[EMAIL PROTECTED] Exchange List admin: [EMAIL PROTECTED] _________________________________________________________________ List posting FAQ: http://www.swinc.com/resource/exch_faq.htm Archives: http://www.swynk.com/sitesearch/search.asp To unsubscribe: mailto:[EMAIL PROTECTED] Exchange List admin: [EMAIL PROTECTED]
