Thank you for posting this issue. I’ve been working on suitecrm8 for couple of weeks.
First I’d like to mention there is no proper documentation for this issue. They just gave the generic guidelines which is useless.
I’ve successfully added my Gmail and office365 account to the profile.
For both type accounts there must be two-factor authentication has to be enabled because for security purpose Google and Microsoft both have removed the option that allow access to less secure apps from the settings.
Then have to create app password from the email account security section.
Then add that app password in the password section