>>> RFC 2821 requires a mail server to choose MX records randomly when the records are the same priority, but to try all if the initial one chosen doesn't work (until it finds one that does work or the pool is exhausted).
Correct. There was, however, an issue early this year (or was it late last year?) where 2K3 SMTP servers were failing to fail over to the next available SMTP servers on the list they receive from a target DNS server. I think this was corrected with a hotfix, but the issue will still exist in a gold, un-hotfixed version. >>>The above means it will try MX of other priorities right (not the other of the same priorities correct?) - sorry just not having a clear word by word answer in the RFC document itself. It will continue to use the highest one, until that one stops responding. As long as the highest-prioritized one continues to accept emails, the originating server will have no need to try another one. HTH Sincerely, Dèjì Akómöláfé, MCSE+M MCSA+M MCT Microsoft MVP - Directory Services www.readymaids.com - we know IT www.akomolafe.com Do you now realize that Today is the Tomorrow you were worried about Yesterday? -anon ________________________________ From: [EMAIL PROTECTED] on behalf of Freddy HARTONO Sent: Sat 12/10/2005 7:07 AM To: [email protected] Subject: RE: [ActiveDir] [Way OT] DNS MX load balancing questions... Hi Michael Thanks for the quick reply. RFC 2821 requires a mail server to choose MX records randomly when the records are the same priority, but to try all if the initial one chosen doesn't work (until it finds one that does work or the pool is exhausted). The above means it will try MX of other priorities right (not the other of the same priorities correct?) - sorry just not having a clear word by word answer in the RFC document itself. One of my vendor is giving me a whitepaper from barracuda appliance that explains how its done, but mentioned that with MX listing below it will provides load balancing AND redundancy (crap to me but now im getting confused myself) http://www.barracudanetworks.com/ns/downloads/Barracuda_WP_MX_Load_Balancing. pdf Is it recommended that the TTL for the domain be set to 0 when using this MX load balancing method? Thank you and have a splendid day! Kind Regards, Freddy Hartono Group Support Engineer InternationalSOS Pte Ltd mail: [EMAIL PROTECTED] phone: (+65) 6330-9785 ________________________________ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Michael B. Smith Sent: Friday, December 09, 2005 8:52 PM To: [email protected] Subject: RE: [ActiveDir] [Way OT] DNS MX load balancing questions... You should have two separate MX records @ IN MX 10 mail1.mydomain.com. @ IN MX 10 mail2.mydomain.com. Mail1 IN A 10.1.1.1 Mail2 IN A 10.2.2.2 RFC 2821 requires a mail server to choose MX records randomly when the records are the same priority, but to try all if the initial one chosen doesn't work (until it finds one that does work or the pool is exhausted). Your proposal below has the problem you describe. ________________________________ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Freddy HARTONO Sent: Friday, December 09, 2005 7:43 AM To: [email protected] Subject: [ActiveDir] [Way OT] DNS MX load balancing questions... Hi All Was just trying to understand something and am getting conflicting results.. If I set the following (or 2 mx of the same priority with 2 differnet a records) Mydomain.com MX 10 mail.mydomain.com Mail.mydomain.com A 10.1.1.1 Mail.mydomain.com A 10.2.2.2 I understand that will provide dns roundrobin but what happened if I shutdown 10.2.2.2, will I lose (logically) 50% of my mail as I do not have another fallback MX?? My understanding is that it does so as the sender mail server will cache the MX record and A record and will only send to there, am I right or am I getting this wrong? If I'm shutting down 10.2.2.2, will the sender mail server retries to 10.1.1.1? (lets assume there's no ttl reconfig to zero) Thanks lots Thank you and have a splendid day! Kind Regards, Freddy Hartono Group Support Engineer InternationalSOS Pte Ltd mail: [EMAIL PROTECTED] phone: (+65) 6330-9785 List info : http://www.activedir.org/List.aspx List FAQ : http://www.activedir.org/ListFAQ.aspx List archive: http://www.mail-archive.com/activedir%40mail.activedir.org/
