Email Deliverability Expert Needed

We are looking for an experienced email deliverability specialist to diagnose an intermittent spam-placement issue affecting legitimate one-to-one business correspondence sent through Zoho Mail from our custom domain, miseagency.com. Our emails sporadically land in spam or junk folders for professional business recipients, including Google Workspace, Microsoft 365 and company-managed email systems. The problem is inconsistent: some messages reach the inbox normally, while others are filtered, even when sent to recipients with whom we have previously communicated. This is not bulk email or a cold email campaign. These are normal, personalized business emails. What we have already confirmed: • SPF, DKIM and DMARC are configured and generally passing • DMARC is currently set to p=none • Zoho support reviewed the account and said the configuration looks correct • Independent seed testing recently achieved 10/10 inbox placement across Google and Microsoft accounts • DMARC reporting showed most Zoho traffic as compliant • Our MX records point entirely to Zoho • Brevo authentication records remain in DNS, but Brevo is not actively sending email • The problem continues sporadically despite successful technical tests We need someone who can go beyond running standard SPF, DKIM and blacklist checkers. The specialist should: • Analyze the complete headers of actual messages that landed in spam • Compare those headers against successful inbox messages • Identify the Zoho outbound IP used for each message • Determine whether specific Zoho shared IPs have reputation problems • Review Google, Microsoft, Proofpoint, Mimecast, Avanan and other gateway signals when present • Evaluate domain reputation, IP reputation, authentication alignment and message-level filtering • Review whether signatures, website links, attachments or existing email threads contribute to filtering • Review our existing DNS records and identify any legitimate configuration concerns • Determine whether the issue is caused by Zoho, our domain reputation, specific recipient systems or email content • Provide a written diagnosis and prioritized action plan Please do not apply if your proposed solution is simply to configure SPF, DKIM and DMARC. Those items have already been configured and tested. We need someone experienced in diagnosing sporadic inbox-placement problems when authentication is already passing. When applying, please answer: 1. How would you diagnose intermittent spam placement when SPF, DKIM and DMARC all pass? 2. Have you previously investigated deliverability problems involving Zoho Mail and its shared outbound IPs? 3. Can you analyze raw Gmail, Microsoft 365 and corporate-security-gateway headers? 4. What information or access would you need from us? 5. Please share an example of a similar issue you diagnosed and what ultimately caused it. We would prefer to begin with a fixed-price diagnostic audit. No DNS or account changes should be made without our approval.