Say that I want to send mail from my own servers at example.com.
As I understand it, I can specify the following SPF record and have any server addressed by an A record under example.com included by the SPF record. So evaluation of mail sent from mailserver1.example.com, mailserver2.example.com would result in a pass:
v=spf1 a ~all
If however I am using an outsourced mail sender say wesendmail.com, I would use an SPF record like this:
v=spf1 include:wesendmail.com ~all
My main question is - If wesendmail.com sends mail from servers at mailserver1.wesendmail.com, mailserver2.wesendmail.com, do I need to include additional SPF records for these servers, or are they captured by the above SPF record?
Also, if I do need to include additional records, how would I find out what their mail servers are? NSLOOKUP domain transfer attempts are blocked by most DNS servers.