If you’re trying to use Gmail to send your Smart E-mails, you will need to enable IMAP on your Gmail account as well as generate an App Password from your Gmail Settings.
Please see this article regarding enabling IMAP on your Gmail settings.
Please see this article regarding generating an App Password in your gmail settings.
When generating your App password under the select app field select other and name the App Password whatever you like.
You may have to go to https://accounts.google.com/DisplayUnlockCaptcha and sign
in with the Gmail username and password, wait 10-15 minutes, then send a
test email before the password will work.
Settings to use for Gmail on the SMTP Server page
Host: smtp.gmail.com
Username: Your username
Password: The App password generated from your Gmail account
Port: 587
Encryption: TLS
If you have done this and the e-mail still isn’t working, you may have been banned from Google due to their strict policies. You should setup a new e-mail box using a different server or through your hosting company.