I realized some specific hostnames will be blocked by the firewall

[jimlinntu]

Ex.
From the client side, if I send a DNS query like this

dig @8.8.8.8 vaaaakaxhiu.mysubdomain.com

will be blocked, while this query

dig @8.8.8.8 abcdefghijk.mysubdomain.com

I spent tons of time finding out about this issue.
Just record in case other people encounter this issue

I launch iodined like this:

./iodined -DD -n <my public IP> -f 10.100.99.1 -c -P 0930100010 b.mysubdomain.com
Debug level 2 enabled, will stay in foreground.
Add more -D switches to set higher debug level.
iodined: IPv6 not supported, skipping
Opened dns0
Setting IP of dns0 to 10.100.99.1
Setting MTU of dns0 to 1130
Opened IPv4 UDP socket
Listening to dns for domain b.mysubdomain.com
RX: client 173.194.93.2, type 1, name abcdefghijk.b.mysubdomain.com
TX: client 173.194.93.2, type 1, name abcdefghijk.b.mysubdomain.com, 5 bytes data

[yarrick]

Sounds a bit like incorrect setup.