Gmail automatically detects the text encoding when you click to view the message. Sometimes gmail makes a mistake to choose the accurate encoding and shows the garbled message. If this is the case, you can choose to view the original message and change the encoding to appropriate one.
To see the original message, click the down arrow next to Reply, at the top-right of the message pane and click Message text garbled?
To change the encoding follow following steps.
Internet Explorer: from the View menu, select Encoding.
Firefox: from the View menu, select Character Encoding.
Safari: click View along the top of your browser, select Text Encoding.
