I just spent a day without being able to send email because I enabled two factor authentication on my work account. That and a complicated gmail setup that apparently appeals to no one else ;)

I forward all my mail from my work, google apps account into my personal gmail account so that all my email is consolidated for reading, filtering, etc. I then use the “Send mail as” functionality to email from my work account. Gmail even allows you to configure alternate SMTP information so that when I send from my work account people don't get a "Sent on behalf of..." in their Outlook.

Well, when I turned on the new two factor authentication for my work email account the smtp password stopped working and this all broke...silently.

No errors when I sent the email, no errors on the SMTP configuration page and worst: all my emails made it successfully into the "sent” folder!

I finally just guessed what must be happening and fixed it.