If Security Defaults has been enabled on your Office 365 account then SMTP Authentication is disabled.
There are 2 options to resolve this:
Disable Security Defaults on the Office 365 account and re-enable SMTP Authentication (and you will probably need to set up a new APP password to use in RDB) or
Set up the Office 365 account to use Modern Authentication instead (which will do away with the need for an APP password.
Access RDB now supports Modern Authentication for sending eMails - if you want to follow this route please use these setup instructions and also please ensure that you set up the required plugins in Access RDB.