How does Microsoft try to send mobile mail to itself?

Does Outlook-iOS-Android keep a mailbox copy on a microsoft server?

Many corporate users who have recently upgraded to iOS 11 have found themselves in limbo. The fact is that after the upgrade, the standard client (Mail.app) stops working with resources on Exchange Server 2016, Office 365 or Outlook.com

Sending a message ends with the error “Cannot Send Mail. The message was rejected by the server. ”
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The problem is that Exchange 2016 uses HTTPS / 2 TLS connections for its clients. When an iOS email application tries to connect to Exchange using ActiveSync, it incorrectly negotiates the connection.

Microsoft confirmed the problem and as a solution offers to install the Outlook for iOS client.

This decision is very controversial, because Outlook does not connect directly to the mail server, and with the accounts entered, the Microsoft server located in the USA connects to your server and most likely downloads a copy of your mailbox to it.

Below is a fragment of the analysis of connection logs from SkypeTime .



In the Russian segment, this issue has not been given sufficient attention, therefore, we provide references to foreign sources.

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We will not judge whether this is legally correct and good, but to increase the level of confidentiality, you can block the connection from these servers to Exchange 2016.

New-ActiveSyncDeviceAccessRule -QueryString "Outlook for iOS and Android" -Characteristic DeviceModel -AccessLevel Block

I hope this information will be useful to someone.