Google Unlock Captcha

Gmail may stop working within Mail.app.  To resolve the issue, use the Google Unlock Captcha.  Quit Mail.app before using the captcha for best results.

https://www.google.com/accounts/DisplayUnlockCaptcha

This may be a necessary step when configuring a Google Apps account on Mail.app.  I needed to run this because I was frequently switching between different ISP’s without closing my mail program.  The following error was reported:

There may be a problem with the mail server or network.  Check the settings for account “Gmail” or try again.  The server error encounteredwas: Too many simultaneous connections. (Failure)