By default Microsoft set a 90 day life span for your Office 365 password. This can be a pain because it's not obvious when this expires, mail flow simply stops to your clients/devices—unless you sign into the service with Outlook Web Access.

If you have deployed AFDS2 then your Active Directory Domain password policy applies also to your Office 365 accounts. If you haven't deployed ADFS2 then you will be subject to the 90 day rule described above.

To disable password expiry for all Office 365 users proceed as follows:

1. Install and configure the Microsoft Online Services Module for Windows Powershell as described in steps 1 & 2 of this link.
2. To disable password expiry for all users run the following commands in Powershell.
• $cred=Get-Credential
• connect-MSOLService -credential $cred
• Get-MSOLUser | Set-MSOlUser -PasswordNeverExpires $true

The credentials provided to the service are those of an Administrator account in the form user@domain.com.