As of today morning (March 26, PST), Google seems to have started blocking outgoing emails sent from some HappyFox accounts which were authenticated (via SMTP) using a Gmail/Google Apps account.
The logs on the HappyFox server were as shown below:
- Set up two factor authentication for Gmail/Google Apps as mentioned here, https://support.google.com/accounts/bin/answer.py?hl=en&answer=180744 If you already have two factor authentication set up for this account, you can ignore this step.
- Set up an application specific password for HappyFox, as mentioned here, http://support.google.com/mail/answer/1173270?hl=en
- Enter the new password from Gmail/Google Apps in your HappyFox account in the Manage >> General >> Outgoing Email Settings section. Note: This setting can be changed only by the Account Administrator in your HappyFox account.