Identified - Unfortunately, there has been issues with the latest patch from Microsoft for Outlook 2016.
This issue has caused some users to receive a constant prompt to input their password.
Until an update is released, please try the below 3 fixes to resolve the issue:

3 Options for Fixing the Outlook Credential Popup Error with Office Apps & Office 365 Desktop Application Customers

Option 1: Manually Update/Add mailbox credentials to Credential Manager & rebuild Autodiscover.xml file
1. Go into Control Panel > Credential Manager > Windows Credentials > Remove/delete any records with the users mailbox address.
2. Download the SaveCredentials.exe tool from here
https://exchange.intermedia.net/customization/downloads/outlooks/SaveCredentials.exe
3. Run the SaveCredentials.exe as administrator
4. Enter the mailbox username and password
5. Next navigate to %LocalAppData%\Microsoft\Outlook\
6. Locate the file that ends in Autodiscover.xml
Note: File may look something like this: f0a4256167a8597a89das6hf01c6bb1b - Autodiscover.xml
7. Delete or rename this file.
8. Open Outlook

Option 2: Revert to an earlier version of Office 2016
Go to the following Microsoft article and follow the steps from here:
https://support.microsoft.com/en-us/help/2770432/how-to-revert-to-an-earlier-version-of-office-2013-or-office-2016-clic

Option 3: Edit registry to ExcludeExplicitO365Endpoint (do at own risk)
1. Open regedit
2. (Highly Recommended) Create backup (https://support.microsoft.com/en-us/help/322756/how-to-back-up-and-restore-the-registry-in-windows)
3. Navigate to HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\AutoDiscover
4. Add new DWORD, give it a name of ExcludeExplicitO365Endpoint and value of 1
5. Restart computer
6. Open Outlook, may be prompted once to enter the users credentials.

Please contact support if the issue persists
support@manageprotect.com
1300 657 500
Jan 16, 16:45 AEDT
MPmail   ? Operational
MPexchange   ? Operational
Soonr / Autotask Workplace   Operational
MParchive   Operational
MPAV   Operational
MPweb   Operational
Backup365   ? Operational
CloudAlly   Operational
Office 365   Operational
Service Desk & Support Systems   Operational
Service & Feature updates   ? Operational
Operational
Degraded Performance
Partial Outage
Major Outage
Maintenance
Scheduled Maintenance
Azure Immediate Maintenance Jan 4, 16:00 - Jan 6, 00:00 AEDT
We are reaching out to notify that Microsoft is carrying out immediate maintenance to Azure Virtual Machines to address the public disclosure of a hardware vulnerability with CPUs.

What does this mean and what is the impact?
Affected Azure Virtual Machines will be restarted.

When did this maintenance begin?
This maintenance began at approximately 7AM Melbourne/Sydney time 4th of January 2018.
We will update once maintenance is complete.

Please note this maintenance is necessary due to a security update that Intel recently released and needs to be applied to any servers using an Intel processor.
Posted on Jan 4, 15:47 AEDT
MPexchange Server Maintenance Jan 25, 02:00-04:00 AEDT
CU7 Server updates will be installed on the Australian MPexchange Servers during this week.
This could cause a possible few minutes of connectivity issues.
In order to avoid disruption, these updates have been scheduled for 2am Australian Eastern Standard Time
No emails will be lost for users on MPmail
Posted on Jan 23, 20:17 AEDT
Past Incidents
Jan 24, 2018

No incidents reported today.

Jan 23, 2018

No incidents reported.

Jan 22, 2018

No incidents reported.

Jan 21, 2018

No incidents reported.

Jan 20, 2018

No incidents reported.

Jan 19, 2018
Postmortem - Read details
Jan 24, 10:46 AEDT
Resolved - This incident has been resolved.
Jan 19, 09:55 AEDT
Monitoring - New Incident Status
Our team has implemented a fix which we believe will resolve the issues that our users were experiencing. We are continuing to monitor to ensure that systems remain stable.

We will update when the issue has been confirmed as resolved.
Jan 18, 17:43 AEDT
Investigating - There have been reports of both MPcloudFS (Workplace &Online) disconnecting.
We are investigating the cause and will update shortly with further information.
Jan 18, 16:14 AEDT
Jan 17, 2018

No incidents reported.

Jan 15, 2018

No incidents reported.

Jan 14, 2018

No incidents reported.

Jan 13, 2018

No incidents reported.

Jan 12, 2018

No incidents reported.

Jan 11, 2018

No incidents reported.

Jan 10, 2018

No incidents reported.