I got an email from "user@example.com" with the Chinese character to Salesforce as inbound message and i replied with Chinese characters from Salesforce to this user@example.com without any issue.

But user@example.com was received in gmail inbox and he opened the email to read but its showing all the Chinese characters as converted to ???????????? questions marks.

He is not able to read the Chinese character content which I replied to his email back.

Please help me what might be the issue is there any issue from Salesforce end or Gmail?