If you are getting this bounceback, you will need to add the server/IP address that did not pass as part of your SPF record. We have an article here for adding SPF/TXT records.
Below is an example of what you would need to add in your SPF/TXT. Please be advised that this is only a guide and you will need to validate your own SPF/TXT record syntax. Ensure that you have made a copy of your SPF/TXT records before attempting this change.
**ip4:**192.168.1.1 (This is just an example IP Address that did not pass)
If you have attempted to add the IP address SPF/TXT record and still have bounce back issues, feel free to contact our friendly customer care team.
To help our customer care team better troubleshoot this issue, please include the following when submitting your support request: Domain, Support code (find it here), Sender Address, Recipient Gmail Address, and the Bounce back Message.