Can I query the name servers used by "relay.plus.net" when sending email ?

[#1]

Hello, just wondering if I can query the name servers used to look up the address of a destination SMTP server when relay.plus.net sends email?
Something like

dig mx mydomain.com @ns1.force9.net

substituting the nameserver used by the relay in place of ns1.force9.net
I found a very old thread asking a similar question here (http://community.plus.net/forum/index.php?action=printpage;topic=71451.0) but it doesn't give a definitive answer. I've tried a few of the IP addresses in that thread but I'd like to be sure I am checking the actual nameserver used when I send email.
I tried

• ns1.force9.net


• ns1.force9.net


• 212.156.13.49 (no answer)


• 212.159.13.50


• 212.159.6.10


• 212.159.6.9

The IP addresses return MX records that I expect to find. The ns1 and ns2 servers do not. (I know it's probably propagation delay but it would be good to be able to test these. Also, strange that some PN servers update quicker than others?)
I cannot find the relevant information in the PN help and support pages.
Thanks.

[#2]

Quote from: starfry

Hello, just wondering if I can query the name servers used to look up the address of a destination SMTP server when relay.plus.net sends email?

No,  you can't I'm afraid.

Quote from: starfry

I found a very old thread asking a similar question here (http://community.plus.net/forum/index.php?action=printpage;topic=71451.0) but it doesn't give a definitive answer. I've tried a few of the IP addresses in that thread but I'd like to be sure I am checking the actual nameserver used when I send email.

The outbound mail platform uses an internal DNS instance that's hosted at our Sheffield data centres (rather than the London data centres where the customer-facing caches are based). There's no point in me disclosing the IP's because they're not accessible to the outside world.

Quote from: starfry

I know it's probably propagation delay...

You're probably right.

[#3]

It's working now 
It took a very long time to propagate given other servers saw the update within minutes. I know you're supposed to allow 24-48 hours, however.
Anyway all is well now.