Information
You can configure this setting to specify how long before passwords expire and users must change them.
Rationale:
The longer a password exists the higher the likelihood that it will be compromised by a brute force attack, by an attacker gaining general knowledge about the user, or by the user sharing the password. Configuring this setting to 0 so that users are never required to change their passwords is a major security risk because doing so allows a compromised password to be used by a malicious user for as long as the valid user has authorized access to the system.
Solution
To implement the recommended state, execute the following PowerShell cmdlet:
Set-MobileDeviceMailboxPolicy default -PasswordExpiration 90