How to set Google Chrome to use Gmail for mailto: links
It seems silly that Google Chrome has no option to default to Gmail for mailto: links and instead a registry hack (or an external program) would be required. In any case, if you’re in that camp, here’s instructions by fellow Tumblr, shonzilla, for how to hack Google Chrome to use Gmail.
Step 1. Copy-paste the entire code snippet below into your text editor and replace username with your Windows username and save it as anyfile.reg.
Windows Registry Editor Version 5.00
[HKEY_CLASSES_ROOT\mailto\shell\open\command]
@="\"C:\Documents and Settings\username\Local Settings\Application Data\Google\Chrome\Application\chrome.exe\" -app=https://mail.google.com/mail?extsrc=mailto&url=%1"
Step 2. Double-click the anyfile.reg to run it and add it to the registry.
Step 3. Done!
Google Chrome team was smart enough not to include version specific information in the file path to chrome.exe meaning this hack will work with any of your future versions of Chrome as well.
Source: shonzilla
