Help understanding SPF record
Lets say my Internet domain is company.com
The zone file for company.com shows
@ IN TXT "v=spf1 a mx include:abc.com include:_marketing.xyz.com ?all"
1. Does this mean that the SMTP servers at abc.com and _marketing.xyz.com are authorised to send emails for company.com?
2. If company.com authorised another 3rd party to send emails, do I just add another 'include:3rdparty.com' to the the SPF record?