Because DNS for iCal can be tricky if you’re editing by hand, a sample may come in handy. These references are to Lion Server, but you can adopt the procedure to other DNS servers.

In Mac OS X Server (and some Linux/Unix servers), the DNS zone file that you edit is in the /var/named directory. The file has the form db.domainname, such as To access it in the Finder, choose Go→Go to Folder and then type /var/named. Open the file and type your additions after the line that begins with $INCLUDE /var/zones/db. Do not delete or change this line.

This INCLUDE line inserts your additions into another similarly named file in /var/named/zone. Although you don’t edit this file directly, here’s a sample of the file in /var/named/zone to give you an idea of what the final looks like. This file contains the DNS entities called A records that are referenced in the SRV records. The text after the semicolons represents in-code comments.

;GUID=<GUID here>
$TTL 10800    ; default expiration time of a record IN SOA (
2009031903  ;Serial
86400     ;Refresh
3600     ;Retry
604800    ;Expire
345600    ;Negative caching TTL
) IN NS ; is the name server for IN A   ;this is the IP address of
ns        A ; IP address of
name       CNAME ns    ;"" is another name for ""
calendar   IN A  ; the IP address for ""
         TXT  "The iCal Server that we're using"
ical     IN CNAME ;"" is another name for "" 86400 IN SRV 0 0 8008

If you have a backup server to use when the first is down, add another calendar line:

calendar2   IN A

Then add another SRV line at the end: 86400 IN SRV 1 0 8008

For SSL, the CalDAV line(s) is 86400 IN SRV 0 0 8443 86400 IN SRV 1 0 8443