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 AEST
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 AEST
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
MPexchange/ Business365 Software Updates Apr 27, 21:00 - Apr 28, 01:00 AEST
Update - Please ignore the previous alert, maintenance is scheduled for 9pm until 1am tonight not in an hour.
Apr 27, 08:08 AEST
Update - An essential Windows update needs to be applied to MPexchange & Business365 servers.

Maintenance Date: Friday, April 27, 2018
Maintenance Window: 9pm to 1am AEST
Expected Downtim(Min.): 0 - servers will be updated sequentially to avoid disruption

Services Impacted: All MPexchange Services
Expected Impact: We will be installing Windows updates that require rebooting your server. The servers will be rebooted sequentially to avoid any disruption.

If you have any issues during this time, please contact support@manageprotect.com
Apr 23, 12:25 AEST
Update - Apologies for the previous status, we realise that 9am to 1pm is an inconvenient time so we are getting this rescheduled to a time outside of business hours.
Updates to follow.
Apr 18, 15:28 AEST
Scheduled - An essential Windows update needs to be applied to MPexchange & Business365 servers.

Maintenance Date: Friday, April 27, 2018
Maintenance Window: 9am to 1pm AEST
Expected Downtim(Min.): 15
Services Impacted: All MPexchange Services
Expected Impact: We will be installing Windows updates that require rebooting your server. Individual services should only be unavailable long enough for patch installation and reboot. Incoming messages will be queued until maintenance is completed.
Apr 18, 12:43 AEST
Past Incidents
Apr 27, 2018

No incidents reported today.

Apr 26, 2018

No incidents reported.

Apr 25, 2018

No incidents reported.

Apr 24, 2018

No incidents reported.

Apr 23, 2018

No incidents reported.

Apr 22, 2018

No incidents reported.

Apr 21, 2018

No incidents reported.

Apr 20, 2018

No incidents reported.

Apr 19, 2018

No incidents reported.

Apr 18, 2018

No incidents reported.

Apr 17, 2018

No incidents reported.

Apr 16, 2018
Resolved - The New Zealand number is now up and running.
Apologies for any issues.
Apr 16, 12:16 AEST
Identified - We are aware of the New Zealand support number being offline and currently working on a resolution.
If you need to get through to support, please use the Australian number: +61 1300 657 500 or chat: chat.manageprotect.com
Apr 13, 13:09 AEST
Apr 15, 2018

No incidents reported.

Apr 14, 2018

No incidents reported.