Just a minor post about an issue some people might have seen (things are fairly quiet in the runup to Christmas).
If you had an issue delivering mail to or from an aol.com address today this post explains why. I don’t currently see anything on AOL’s postmaster blog with regards to the outage.
At approx 07:00 GMT today aol appear to have removed the MX record for aol.com
Here we lookup their nameservers – the servers that hold all the DNS records for their domains
$ dig NS aol.com +short
dns-02.ns.aol.com.
dns-01.ns.aol.com.
dns-06.ns.aol.com.
dns-07.ns.aol.com.
So (during the outage) lets ask one of those DNS servers where the mailserver for the domain aol.com is – we’re querying their nameserver directly:
$ dig MX aol.com @dns-02.ns.aol.com.
; <> DiG 9.7.2-P3-RedHat-9.7.2-1.P3.fc13 <> MX aol.com @dns-02.ns.aol.com.
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 48542
;; flags: qr aa rd; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0
;; WARNING: recursion requested but not available
;; QUESTION SECTION:
;aol.com. IN MX
;; AUTHORITY SECTION:
aol.com. 300 IN SOA dns-02.ns.aol.com. hostmaster.aol.net. 304268691 43200 60 1209600 300
;; Query time: 115 msec
;; SERVER: 205.188.157.232#53(205.188.157.232)
;; WHEN: Tue Dec 21 10:07:02 2010
;; MSG SIZE rcvd: 89
So in short, there’s nothing – nowhere to deliver mail and so the domain will not handle mail. This means mail to @aol.com addresses was returned as unroutable and mail from that domain was rejected by basic sender verification (e.g. does the domain you’re claiming to be from actually exist as a mail domain?).
It appears to have been fixed at 10:30 GMT, the mailservers are now listed:
$ dig MX aol.com @dns-02.ns.aol.com. +short
0 mailin-04.mx.aol.com.
0 mailin-01.mx.aol.com.
0 mailin-02.mx.aol.com.
0 mailin-03.mx.aol.com.