Dns sometimes fails using Google DNS / automatic dnssec

[MailPlus| David Hofstee <david () mailplus nl>]

Hi,

We've been seeing automatic RRSIG records on Google DNS lately, the 8.8.8.8 en 8.8.4.4. They are not always provided. 
They cause problems for some of our customers in a weird way I cannot explain. For them these records do not resolve 
but I cannot reproduce it.

So when I run dig command

dig @8.8.8.8 m1.mailplus.nl

it often provides the RRSIG record (but e.g. the TXT record will not be signed). I've heard that DNS may fall back to 
TCP and/or may be filtered by firewalls if UDP is over 512 bytes. However, the request is not that long, about 200 
bytes if I interpret the answer correctly.

Can someone come up with a good explanation why a tiny percentage of our customers cannot resolve (some of) our domains?

Btw, our nameservers (transip.nl) only provide DNSSEC records if explicitly asked. What is standard here?


Thanks,

David Hofstee