I'm trying to get IT to configure the subdomain we've chosen in the DNS settings for a Sender Authentication Package. They've come back to me and said they need to know the IP address for the subdomain to point to. I didn't think this was a requirement and it's not mentioned in the SAP help pages, so do we need to provide this? I know we get a dedicated IP address with the SAP but how do I find out what this is?
You cannot just point the domain to an IP address. There are two ways of configuring SAP domain. The most common one is delegating the sub domain to the NS servers of Salesforce/ExactTarget.
The process is well described in this article.
Below is a sample DNS entry for example.com, delegating news.example.com as sub domain:
Delegate news.example.com to Salesforce Marketing Cloud news IN NS ns1.exacttarget.com news IN NS ns2.exacttarget.com news IN NS ns3.exacttarget.com news IN NS ns4.exacttarget.com
You can also choose to self-host your domain, configuring all the single DNS records, but these are specific to each account and will be provided as a zone file from Salesforce, if you select the option for self-hosting when submitting the SAP form.
An example of such settings can be found here.