Newbie Question : EMail servers and MX records
julien at sype.org
Fri Jan 10 23:40:42 UTC 2003
i will try to answer you ...
paul williams wrote:
> I'm not too hot on DNS and that kind of thing. My understanding is
> that DNS is a globally connected list which allows host names to map
> to IP addresses.
> How does this work for mail servers using MX entries in the DNS ?
> For instance, we've got a small email server here which processes our
> email for xyz at treysta.net. I understand that theres a DNS entry for
> mail.treysta.net somewhere which points to our mail server.
> So, if someone, say xyz at abc.com sends a mail to me at treysta.net, how
> does it all work. Does it search the DNS for an MX entry for
> treysta.net and then direct it to our mail servers IP address ?
> Whys it called mail.treysta.net ? Or could it be anything.treysta.net
> just needs to be an MX entry ?
just need to be an mx record
> What happens if email sent is unable to connect to the IP address
> pointed at mail.treysta.net ? Does email get bounced ?
no, most if not all mail transport agent (servers) have timers to
re-try sending the email for a couple of days... so if it can't reach
the mail server
after x times for let's say 2 days .... it comes back to the sender
saying the mail server couldn't been reach...
finaly: i'll give you an example of this without the mail in mail.host.org
if you have any question ask ....
; <<>> DiG 8.3 <<>> microsoft.com mx
;; res options: init recurs defnam dnsrch
;; got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 2
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 6
;; QUERY SECTION:
;; microsoft.com, type = MX, class = IN
;; ANSWER SECTION:
microsoft.com. 2H IN MX 10 maila.microsoft.com.
microsoft.com. 2H IN MX 10 mailb.microsoft.com.
microsoft.com. 2H IN MX 10 mailc.microsoft.com.
;; ADDITIONAL SECTION:
maila.microsoft.com. 2H IN A 22.214.171.124
maila.microsoft.com. 2H IN A 126.96.36.199
mailb.microsoft.com. 2H IN A 188.8.131.52
mailb.microsoft.com. 2H IN A 184.108.40.206
mailc.microsoft.com. 2H IN A 220.127.116.11
mailc.microsoft.com. 2H IN A 18.104.22.168
;; Total query time: 86 msec
;; FROM: sype.org to SERVER: default -- 192.168.1.100
;; WHEN: Fri Jan 10 18:37:51 2003
;; MSG SIZE sent: 31 rcvd: 193
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