We have been having the same issue since yesterday and have found a workaround that works for us. It's fairly simple, so worth at least trying out.

One big caveat: this only works if you use Gmail, but have a custom domain that you use through Gmail. In other words, if your email ends in @gmail.com, this won't work. If you use Gmail, but your email address is @yourdomain.com, it will work.

Basically, we reverted to using the old, less advanced way of connecting to Gmail.

• Go to Edit, Preferences, Send Forms.
• Delete your email account.
• Add a new email account.
• Enter your email address as the "Email ID"
• For Email provider, DO NOT select Gmail. Instead choose "Others"
• Servername: smtp.gmail.com
• Port: 587
• Check the SSL/TLS box
• Click Okay.

For this to work, you will also need to create an "App Password" for quickbooks in your gmail account. Instructions to do that are here: https://support.google.com/mail/answer/185833?hl=en

Your "App Password" will only be for use when email from Quickbooks and is different than the password you use to log into Gmail.

The next time you try to email from QB, it will prompt you for your email password. When it does, use the "App Password" we just created.