"Send to" looks for an email client and since Thunderbird has been installed, it selects that. My guess is that you normally go to the Gmail website to work with your email. Unfortunately, a browser won't necessarily be recognized as standing in for an email client. You could set up Gmail in Thunderbird so it does "just work" but you'll have to enable regular email in your Google account and probably have to go through a setup that involves getting a temporary password from Google to validate Thunderbird. You could uninstall Thunderbird, but to make googlemail via a browser the default mailer, I think you'd need to install Google Notifier, which acts as the default mailer and opens your Gmail website for when using "Send to" . Or you could stop using "Send to" . Open Gmail in your browser, start a new message and use the tools provided there to attach or upload your pictures.