Using Outlook for Android in business environments for email and scheduling
I have On Premisses Exchange 2010 and my users have Outlook App in Android and IOS, and also have problem.
I found this article, when my Intermediate Certificated have problem.
https://www.theregister.co.uk/2018/02/07/beware\_the\_coming\_chrome\_certificate\_apocalypse/
https://blog.mozilla.org/security/2018/03/12/distrust-symantec-tls-certificates/
I ask Symantec, and they confirm the problem.