Gmail Email Receiving Issue Troubleshooting

I'm facing a unique email receiving issue with my Gmail account. While I can receive emails from most addresses, there are a few specific addresses from which I'm not getting any emails - they seem to be mostly microsoft addresses (outlook, msn, etc) and when there's a thread of emails. I have already gone through various troubleshooting steps but haven't been able to resolve the issue.

Key requirements:
- Diagnose the root cause of the issue: The freelancer needs to identify why these specific email addresses are being blocked or not reaching my inbox.
- Implement corrective measures: Based on the diagnosis, the freelancer should then implement the necessary changes to ensure I start receiving emails from these addresses again.

The ideal freelancer for this project should have:
- Extensive experience with Gmail: Proficiency with Gmail’s settings and configuration is a must for this project.
- Troubleshooting skills: The freelancer should be adept at identifying and resolving email-related issues.
- Excellent communication: As part of the troubleshooting process, the freelancer may need to communicate with the senders of the affected emails.

Please provide a clear overview of your approach to this issue, and how you intend to tackle and resolve it.