We are running Acumatica 2020 R1, and have this working. I am not sure if it will work in 2019R1, but you can give it a try.
Our environment is synced with Local AD through Azure AD Connect. We have seamless SSO enabled with Passthrough Authentication, and the group policy trust enabled for the workstations. This allows the users to sign into office 365 from their domain controlled computers.
https://learn.microsoft.com/en-us/azure/active-directory/hybrid/how-to-connect-sso-quick-start
When we enable automatic signon through AzureAD in the web.config, it works like a charm. We had issues in previous versions of Acumatica with our ADFS deployment. To enable automatic SSO in Acumatica you can modify your web.config:
<externalAuth authUrl="Frames/AuthDock.ashx" silentLogin="Federation" externalLogout="True" selfAssociate="True" instanceKey="" claimsAuth="False">
I would give this a try on off hours to see if it works with Outlook, and maybe change your production instance to sign in this way. You can always get to the login page by visiting https://acumaticainstance/Frames/Login.aspx?SilentLogin=None
Maybe setting auto signin will fix outlook and be easier for those users, and be more beneficial than the non-azure users?