Microsoft and Google are changing the connection requirements for third-party applications (like Incisive) to send emails through their SMTP (out-going) email services.  These connections now require a token to be requested and passed back to Incisive application, instead of just requiring your encrypted login & password, for the Microsoft & Google services to allow the email to go through.

Previously, Gmail had an option to allow 'less secure' applications to send emails through their SMTP service, however this option has now been disabled.  There is a different security option called 'App Password' which may work for you, but is only available if you have 2FA authentication enabled on your Google account.

Google Support provides the following knowledgebase article https://support.google.com/accounts/answer/185833?hl=en

Enter your gmail address and the newly generated password into Setup > Provider > Email