Email Deliverability Specialist

I am looking for an experienced Email Deliverability Specialist, DNS Expert, or Email Authentication Specialist to diagnose and permanently fix an email delivery issue occurring on a WordPress website.
This is NOT a website design project and is likely NOT a major development project. I am specifically looking for someone with strong experience in:
DMARC
SPF Records
DKIM
SMTP Configuration
Email Deliverability
DNS Records
WordPress Email Routing
Post SMTP (WordPress Plugin)
GoDaddy Hosting
The Problem
We are receiving email bounce-back errors from our website.
The website uses:
WordPress
Post SMTP
GoDaddy Hosting
Custom domain email addresses
The issue appears to occur when certain form submissions contain Yahoo email addresses. Based on my initial review, it may be related to DMARC validation and how the "From" and "Reply-To" fields are being handled by the website or SMTP configuration.
What I Need
Review the current email routing and SMTP configuration.
Review SPF, DKIM, and DMARC records.
Identify the root cause of the rejection.
Implement the proper fix.
Test and verify successful email delivery.
Provide a brief explanation of what was changed.
Recommend any additional email authentication improvements if needed.
Important
Before applying, please tell me:
What you believe is the most likely cause based on the error message below.
Whether you believe this is:
a DMARC issue
an SPF issue
a DKIM issue
a WordPress configuration issue
an SMTP issue
or a combination of the above.
Approximately how long you believe it will take to diagnose and fix.
Bounce Back Error Details
Recipient:
promotions@imcfresno.com
Error Message:
550 5.7.509 Access denied, sending domain yahoo.com does not pass DMARC verification and has a DMARC policy of reject.
Additional Header Information:
Authentication-Results:
spf=pass
dkim=none (message not signed)
dmarc=fail action=reject
header.from=yahoo.com
Mailer:
Postman SMTP 3.9.4 for WordPress
SMTP Relay:
GoDaddy / SecureServer
Deliverables
The project will be considered complete when:
Emails are successfully delivered.
No DMARC rejection errors occur.
SPF, DKIM, and DMARC are properly configured.
Testing confirms the issue has been resolved.
A brief explanation of the root cause and fix is provided.
Access Available
I can provide access to:
WordPress Admin
Hosting Account
DNS Management
SMTP Configuration
Any other information needed to troubleshoot the issue
Budget
Please provide a fixed-price quote along with your assessment of the likely root cause.
I am looking for someone who specializes in email deliverability and authentication rather than a general web developer.
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