Look very closely at the email address to verify spelling, then use the envelope "Correct" option to make changes. Here is what I do when I see an issue and it is not apparent what is wrong. I copy the email address form Outlook or the email program and paste it into Notepad, then I take the email address from the envelope, copy and paste into Notepad and then compare. Simple things like a missed letter or incorrect domain extension such as adding .COM instead of .EDU can cause failures.

Appreciated for your reply😊

I have compared the address in envelope and in e-mail, and it is totally same. I can reach the PERSON by copying his address from the envelope and pasting it in e-mail.

I just found that this error occurs also if I set another person as signer, who is in the same company of the PERSON. So I am wondering this might be caused by mail server setting of the PERSON's company.

More than happy if someone give me any advice.

It absolutely could be a rejection by the Recipients email servers, spam filters, firewall or other device designed to reduce phishing or spam. When I have this type of issue, I start with a DocuSign case providing the Envelope ID and the email of the Recipient. DocuSign support can provide more details on the reason for the rejection. Then check with the Recipient to see if they can involve their IT department to troubleshoot network issues as needed.

Really appreciated for your quick and kind advice.

I dont see a "correct" option

Are you the "Sender" of the envelope or shared with the DocuSign User who sent the envelope? If not you would not see the "Correct" option if you were just a Recipient on the envelope.