DNS weirdness with cname lookups

Good morning,

Set up: I have MacMini Server running 10.6 and three Mac clients (two with Snow Leopard and one with Lion). All software updates are applied. Two of the clients are connected with ethernet cable and one is connected over the Airport. I use the server to provide DHCP for clients but one client uses a manual ip address. I'm also running DNS with one primary zone for the server (basically). Forwarder ip addresses are set to 8.8.8.8/8.8.4.4 and recursive queries are accepted from "localnets". This set up has been in place working for many months.

Problem: Yesterday morning, my wife, using her computer (one of the 10.6 clients), complained that her mail was not coming in. We use Apple Mail to connect to Gmail using imap. Mine continued to work fine even though the set up is basically the same but I use the Lion client. There were not any problems browsing and she could get the mail through the Gmail web site, just not imap.

Actions: Through troubleshooting I determined the problem to be associated with DNS lookups of cname records. Lookup of gmail-imap.l.google.com works fine, lookup of imap.gmail.com fails.

Tims-Mac-mini:Programming tim$ dig imap.gmail.com

; <<>> DiG 9.7.3-P3 <<>> imap.gmail.com

;; global options: +cmd

;; connection timed out; no servers could be reached

=====================

Tims-Mac-mini:Programming tim$ dig gmail-imap.l.google.com

; <<>> DiG 9.7.3-P3 <<>> gmail-imap.l.google.com

;; global options: +cmd

;; Got answer:

;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 6239

;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 4, ADDITIONAL: 0

;; QUESTION SECTION:

;gmail-imap.l.google.com. IN A

;; ANSWER SECTION:

gmail-imap.l.google.com. 231 IN A 173.194.77.108

gmail-imap.l.google.com. 231 IN A 173.194.77.109

;; AUTHORITY SECTION:

google.com. 98135 IN NS ns1.google.com.

google.com. 98135 IN NS ns4.google.com.

google.com. 98135 IN NS ns3.google.com.

google.com. 98135 IN NS ns2.google.com.

;; Query time: 422 msec

;; SERVER: <local_DNS_server_ip>#53(<local_DNS_server_ip>)

;; WHEN: Sat Apr 28 07:14:17 2012

;; MSG SIZE rcvd: 145

Initally, this behavior was only on the 10.6 clients but is now also present on the Lion client.

I have used dscacheutil to flush the cache on clients and the server multiple times but it doesn't seem to help.

Yesterday afternoon, I threw up my hands and rebooted the server. It worked (I thought) so I decided it was a mystery I would not understand.

But, the problem returned last night. A lookup of imap.gmail.com works from the server but not from any of the clients.

Does anyone know what is going on? What can I test next?

Thank you in advance.

Tim