Here is the screenshot

I am wondering which server posted that message to you. It seems an odd thing for an SMTP server to say, but if it somehow comes from the correspondent's email (IMAP/POP) server then there is little you can do about it other than re-check the addressee's address.

If you'd like to post your settings here, someone may be able to spot if anything has gone awry there.

Please add the troubleshooting information to your post. To find the Troubleshooting information:

• Open Help (or click on three-line-icon and select Help);
• Choose Troubleshooting Information;
• Clear the check box "Include account names";
• Use the button Copy to clipboard to select all;
• Paste this in your post.

Is the correspondent correctly entered into your Address Book? "Green, A" would not in itself be a valid email address (but of course this may be a legitimate nickname or display name.)