Gmail’s new labs feature automatically appends your location to your e-mail signature. So, now whether you are in NY or CA, message recipient will get to know your location automatically from your e-mail signatures.

Also, you can keep track of where you were when you sent that message.

After enabling this feature in Labs settings, head over to Settings in Gmail and look for Signature settings and tick mark the checkbox that says "Append your location to the signature".

Next time you compose a new message, the signature with location will be added to your message.

This feature uses Google Gears’s Geolocation API to detect your location based on your external IP address. The location might not be always accurate. You can always edit your location if Gmail fails to detect your exact location.