+++ Logu [linux-india] <13/12/01 19:00 +0530>:
> Is there a way to check the validity of an e-mail, not simply the syntax but
> it should check if the domain and the user in that domain exists.(atleast
> the domain).
> Waiting for your grateful reply.
Easily enough for whether the domain exists ...for the purpose of mail
delivery there must be a proper set of MX and A records (where the MX doesn't
point directly to an IP, or to a CNAME, or to an unresolvable host)
$ dig hserus.net MX
; <<>> DiG 8.3 <<>> hserus.net MX
;; res options: init recurs defnam dnsrch
;; got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 4
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 3
;; QUERY SECTION:
;; hserus.net, type = MX, class = IN
;; ANSWER SECTION:
hserus.net. 4H IN MX 0 hserus.net.
;; AUTHORITY SECTION:
hserus.net. 4H IN NS dns4.interserver.net.
hserus.net. 4H IN NS dns5.interserver.net.
;; ADDITIONAL SECTION:
hserus.net. 4H IN A 66.78.36.146
dns4.interserver.net. 1D IN A 216.10.26.20
dns5.interserver.net. 1D IN A 216.10.26.21
;; Total query time: 294 msec
;; FROM: mjollnir.outblaze.com to SERVER: default -- 192.168.2.1
;; WHEN: Fri Dec 14 10:42:45 2001
;; MSG SIZE sent: 28 rcvd: 142
Here, a domain doesn't exist - so you just get SOA records if any, or an
NXDOMAIN
$ dig example.com MX
; <<>> DiG 8.3 <<>> example.com MX
;; res options: init recurs defnam dnsrch
;; got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 4
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0
;; QUERY SECTION:
;; example.com, type = MX, class = IN
;; AUTHORITY SECTION:
example.com. 1D IN SOA VENERA.ISI.EDU. iana.ISI.EDU. (
950301 ; serial
12H ; refresh
1H ; retry
2W ; expiry
1D ) ; minimum
;; Total query time: 217 msec
;; FROM: mjollnir.outblaze.com to SERVER: default -- 192.168.2.1
;; WHEN: Fri Dec 14 10:43:07 2001
;; MSG SIZE sent: 29 rcvd: 84
Here, MX forwards to an unresolvable host - note the IP 192.168.10.1 of
nomail.o0o.net (oh zero oh ...)
$ dig pmail.net MX
; <<>> DiG 8.3 <<>> pmail.net MX
;; res options: init recurs defnam dnsrch
;; got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 4
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 3
;; QUERY SECTION:
;; pmail.net, type = MX, class = IN
;; ANSWER SECTION:
pmail.net. 1D IN MX 10 nomail.o0o.net.
;; AUTHORITY SECTION:
pmail.net. 1D IN NS ns2.o0o.net.
pmail.net. 1D IN NS ns1.o0o.net.
;; ADDITIONAL SECTION:
nomail.o0o.net. 1D IN A 192.168.10.1
ns1.o0o.net. 1D IN A 66.51.203.2
ns2.o0o.net. 1D IN A 66.51.203.3
;; Total query time: 5231 msec
;; FROM: mjollnir.outblaze.com to SERVER: default -- 192.168.2.1
;; WHEN: Fri Dec 14 10:44:52 2001
;; MSG SIZE sent: 27 rcvd: 138
--
Suresh Ramasubramanian <----> mallet <at> efn dot org
EMail Sturmbannfuhrer, Lower Middle Class Unix Sysadmin
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