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Hi Neil, On Mon, 15 Nov 2004 21:32:32 +0000 UTC (11/15/2004, 3:32 PM -0500 UTC my time), Neil White in part wrote:
Cannot help you unless you provide true info.
N> I would love to, but my employers are paranoid so I cant Im afraid.... I understand... If you have DNS tools, you can use dig or some such to find all MX records published to the net, e.g. dig mx foo.com
Bottom line, in today's times, you do not need a backup MX, IMO... period. Every modern MTA will keep mail in its sending queue (for the life of the queue, usually a week), and keep retrying if the receiving server is down.
N> This is interesting....I can see where you are coming from, but why do N> so many other providors have backup MX ? they really don't, very few do... let's take for example AOL... One of the largest email users and ISPs. What do they send, 20, 30, 50 million emails a day minimum? Probably receive as many, if not more per day. their records show: ; <<>> DiG 8.3 <<>> mx aol.com ;; res options: init recurs defnam dnsrch ;; got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 2 ;; flags: qr rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 0, ADDITIONAL: 0 ;; QUERY SECTION: ;; aol.com, type = MX, class = IN ;; ANSWER SECTION: aol.com. 1H IN MX 15 mailin-02.mx.aol.com. aol.com. 1H IN MX 15 mailin-03.mx.aol.com. aol.com. 1H IN MX 15 mailin-04.mx.aol.com. aol.com. 1H IN MX 15 mailin-01.mx.aol.com. As you can see, one of the world's largest ISPs, does not use back up MX. All have the same time value on MX, there are no backup MXs. What you are seeing are 4 mail scalable server stations at different locations which are dividing the workload (in and outbound SMTP) after load balancing or round-robin. Of course, they may be subdivided internally, but externally on the net, these are their MX addresses. N> I am not trying to be argumentative or anything, but just wonder if N> you have any information backing this up? As the above example. It is all published on the net, just pick any ISP, or large organization and "dig" the DNS info. I am sure you can search google on why backup MX is not needed. N> If backup MX is not needed, why does everyone still use it ? everyone does not use it <g> It is *not* necessary... Some have it published, but do not use it except for special circumstances, or use it to only forward email from other authorized IP addresses, and reject all others, etc.. so they do not use it truly as a backup MX. This can be used for several purposes, least of which is a backup MX. N> Thanks for all of your points... its making more sense now you are welcome... N> (Im learning still) hee, hee... aren't we all... That's what makes life interesting. -- Gary