I send emails on behalf of customer1.net from mailer.mycompany.com. We also manage bouncebacks by setting the return-path on the envelope to setting it to bouncemgmt.mycompany.coom which in this case is the same server.
The SPF record for my customer is:
customer1.net IN TXT "v=spf1 a mx a:mailer.mycompany.com mx:bouncemgmt.mycompany.com ip4:18.104.22.168 ?all"
The header when sending a few emails from our application on behalf of our customer is:
Received-SPF: pass (google.com: domain of firstname.lastname@example.org designates 22.214.171.124 as permitted sender) client-ip=126.96.36.199;
And even though it said that it passes, it ends up in the outlook junk folder. Our main concern is that the actual SPF record is configured correctly.
We are using the following Website to configure it: openspf.org