Email Deliverability Troubleshooting

I am experiencing email deliverability issues with my booking platform. System emails, such as invoices sent from my 365 exchange info@ email, are frequently landing in spam/junk folders. While Outlook seems to work, Gmail results in consistent delivery to the Junk folder.

The scope of the project includes diagnosing and resolving this issue to ensure reliable delivery of system emails.

Ideal skills for this job include:
- Proficiency with 365 exchange email systems
- Experience with booking platform email integration (we use BookNow- part of SalesForce)
- Knowledge of email deliverability best practices
- Familiarity with DMARC and other email authentication methods

We have added SPF records. DKIM is set up. Everything looks relatively good when you use MX toolbox to check the DNS settings but the booking platform that is built on Salesforce will not send invoices etc
Some of the responses from our email marketing that uses Zoho campaigns is getting stuck in Quarantine. Quarantine reports suggest a spoof DMARC but it has been set and MX Toolbox / Zoho campaigns etc suggest is it in correctly.
So we have a need for an experienced 365 exchange/DNS/email deliverability expert to help troubleshoot.

Please, no time wasters. I am looking for a professional who can get this sorted promptly.