I'm confused on how I should set up SPF records for my multiple domains. Here is my configuration:
the setup is:
(a) domain1.com points to server1
(b) mail.domain1.com points to server2
(c) domain2.com is a vhost in server1
(d) domain3.com is a vhost in server1
(e) and so on..
I want the SPF record to be set up so that domain1.com, domain2.com, domain3.com are authorized to send emails using mail.domain1.com. I'm confused on wether to put the SPF record on each domain, or on the main server only.