AWS SES receiving email - only few emails are received that are sent from verified domain only

Good day Community,

I have an SES email receiving rule that puts the incoming email to S3.

What Works:

• It works well if the email is sent from the SES verified domain in my account by using the "Send Test email" in SES console.
• The received emails are stored in S3 bucket.

What Does Not Work:

• However, when I send an email using my personal gmail account, the email never got stored in S3.
• The mail client (Gmail) with the verified domain is still able to receive the incoming email.

Setup

• AWS SES account is still Sandbox (us-east-1) not production
• MX priority is set to 1 which is same priority as Gmail
• The subject and content of the email is the same - just plain text "Hello World".

Problem

How can I configure SES to receive emails coming from "external" emails like gmail?