Question: When testing my Office365 settings in admin > channels > email > edit > test settings I am getting an error "Your account details are inccorrect", I know that my credentials are correct but I am still getting the error.

Answer:
Microsoft has disabled Basic Authentication for Azure AD logins, this means that Office 365 mail accounts must use OAuth2 in order to login to send and receive emails. You can read their article on this here.
Any newly created Office365 logins will require OAuth2 setting up, and Microsoft are currently in the process of updating their exsiting O365 customer base to use Oauth with no warning.
We have documentation on how to setup OAuth2 here, and how to use an O365 account with Deskpro On-Premise here.
Additional Questions:
What is OAuth2 and how does it work? OAuth is used soley for authentication. It hands over the job of logging in to the email account to the provider (i.e. Office365). It uses a token which we can use to authenticate when we try to send emails, so we do not hold any of the user’s login credentials such as their email address or password. When sending or receiving emails we use the token generated by the OAuth to authenticate the user, then the email itself is sent by the usual transport method.
What infomation is stored by OAuth and for how long? OAuth only stores the Application ID, the Secret, and the tokens which are generated by the application (which are regularly replaced by the application) long term.
Does OAuth use encryption? The OAuth request is encrypted using the certificate which is generated during the setup of the application.
What level of access is required by Deskpro? We fully expect any accounts which are logged in through OAuth to simply have a mail account and no further credentials. We also advise users to have a separate mail account specifically for Deskpro to monitor.
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