Outlook mobile app for iOS starts showing "External Recipients Tips" for Internal Users

[gen-san]

HI Team

I have seen there was an update on March 21st, 2019 Outlook Mobile App for iOS. 

Since then Outlook for iOS starts showing "External Recipients Tips" for "Internal users" which I set up as Remote Domain in Exchange Online. It was set Remote Domain settings "IsInternal" is $True.

It is not showing as "External Recipients" from my Win10 Outlook (2016) which is good.

For Example for Mail Tips

- Outlook2016

1.  Email send from test0@contoso.com   to   test1@contoso.com    -> Not showing "External Recipients Mail tips"

2.  Email send from test0@contoso.com   to   test2@us.contoso.com  ->  Not showing "External Recipients Mail tips" (Remote Domain "IsInternal" $True)

3.  Email send from test0@contoso.com   to   test3@ExternalDomain.com ->Showing "External Recipients Mail tips"

- Outlook for iOS

4  Email send from test0@contoso.com   to   test1@contoso.com    -> Not showing "External Recipients Mail tips"

5. Email send from test0@contoso.com   to   test2@us.contoso.com  -> Showing "External Recipients Mail tips" (Remote Domain "IsInternal" $True) 

6. Email send from test0@contoso.com   to   test3@ExternalDomain.com -> Showing "External Recipients Mail tips"

How can I make it not showing (No 5 )"External Recipients Tips" in the Outlook for iOS App? 

Please advise.

[#2]

@gen-san 

We have what might be a similar issue.  I've been able to prove that mail flow between internal users is passed as expected UNLESS they are using the Outlook mobile app, which mysteriously applies mail flow rules as if the sender is someone outside the domain.  

Sender@abc.com to Recipient@abc.com with HTML attachment using Outlook desktop client:  OK

Sender@abc.com to Recipient@abc.com with HTML attachment using Outlook mobile app:  Blocked by exchange\mail flow\rules attachment rule.

Maybe this is a temporary bug?  You would think authenticated exchange users would be treated as internal senders regardless of client used.

Ron