When I send out emails using Gmail, is my IP address being recorded? Can the recipient of my Gmail message know my IP address and thus infer where I am located?
Send yourself an email (at a non-gmail email address) via gmail and read the "full header" or "message source", especially "X-Originating-IP".
Compare this with your own external IP address (google [my ip is]).
The header of an email which I sent from my own gmail address to my own gmail address ("Show Original") did not contain an originating IP address, or any IP address except a reserved address in the 10.x.x.x range (in other words no IP address that would be identifiable as mine).
Then, I sent an email from my gmail address to myself at another email provider. The header of this email had an X-Originating-IP address which resolves to Google, Inc. It contained several IP addresses, none of which were identifiable as mine.
In appropriate cases a subpoena, search warrant or other lawful process directed to Google, Inc. would, of course, unmask your IP address and reveal your general location (and more legal process would force your ISP to reveal the IP address subscriber's name and address).
Your IP address was recorded by Google when you sent the email, and by God knows what other spooks inhabit the interwebs between you and your ISP, and between your ISP and Google, but it was not sent to your mail recipient(s).
Google/Gmail strips the originating IP address (among other things) from outgoing messages - so the receiver cannot see the IP to indicate where you are, or more correctly, where the email originated from.
***update - seems if the email is sent between gmail accounts the originators IP is in there...
Other online email services (Yahoo...) leave the originating IP in the header. You could use a VPN to obfuscate the IP.
For privacy this IP stripping is great, for doing illegal stuff, then don't use email.
2014, June 26: I used the Gmail web interface to open an email sent from a Gmail account to a Gmail account, clicked next to the "Reply" icon, and selected "Show original" and I was able to see the originating IP. In this case it was the IP address assigned from my ISP to my router at home (which I needed because it changed and I wasn't using any dynamic DNS tool)
Select the message you want to view, click on "More" (beside the reply button) and select "Show original". It will open a new window with the email header information. Under the "Received" section will be your IP address and all the corresponding mail transfer agent (MTA) information that the email traveled through.
So the recipient may roughly guess your geographical location via your IP address information provided you are not using either VPN or webmail. If the sender had used Google webmail, then the IP address will point to the Google's mail service rather than your IP address. A further check with Google or your VPN service provider is needed to determine the IP address from their log files. Finally, with the IP address, cross referencing from your ISP's DHCP records can determine exactly who sent the email.