[Solved] 550 Sender verify failed (in reply to RCPT TO command)

I've tried many way to solve this problem and I found it.


I my case, I host website on my own VPS. However, I use QQ Mail to handle my domain email. Whenever I sent email to my other email address on the same server, I got the following error in my Email Delivery Report in WHM.

550 Sender verify failed (in reply to RCPT TO command)