I just want to clarify the +a part of an SPF record since I have an idea how this works but I am unsure.
spf record for example.com
v=spf1 +a -all
My current understanding is that if there is a valid a record for the server it will be accepted.
A: example.com 123.456.789.12
the IP address above would be a valid sender for example.com because of +a.
However I am unsure about sub-domains and how this works.
A: server-1.example.com 123.456.789.13 A: server-2.example.com 123.456.789.14
Would these IP addresses also be allowed to send as example.com because of the +a part of the SPF record?