After updating Exchange 2013/2016/2019 you might get an error when trying to open OWA or ECP. This happens because of an expired OAuth certificate.

Open Exchange Powershell and check if the certificate has expired:

Get-ExchangeCertificate (Get-AuthConfig).CurrentCertificateThumbprint

If the certificate has expired, create a new one (do not forget to change the domain name):

New-ExchangeCertificate -KeySize 2048 -PrivateKeyExportable $true -SubjectName “cn=Microsoft Exchange Server Auth Certificate” -FriendlyName “Microsoft Exchange Server Auth Certificate” -DomainName “ajni.it“

Set the new certificate for OAuth:

Set-AuthConfig -NewCertificateThumbprint <ThumbprintFromStep1> -NewCertificateEffectiveDate (Get-Date)
Set-AuthConfig –PublishCertificate
Set-AuthConfig -ClearPreviousCertificate

Restart the Exchange IIS App Pools:

Restart-WebAppPool MSExchangeOWAAppPool
Restart-WebAppPool MSExchangeECPAppPool

If you still get the error in OWA/ECP, you either have to wait a couple of hours (some people have reported that they had to wait for up to 6 hours) or change the time zone of the Exchange server to UTC (Universal Coordinated Time).

References:

https://www.frankysweb.de/exchange-server-owa-und-eac-starten-nicht-nach-installation-der-juli-updates/

https://support.microsoft.com/en-us/topic/you-can-t-access-owa-or-ecp-after-you-install-exchange-server-2016-cu6-88b3fe67-5f97-a8a2-8ed8-70034ff15761

If you are having problems with Citrix Studio and Storefront being very slow on load, this article might help.

On Studio/Storefront startup, Windows tries to verify code integrity by checking the certificate revocation list (CRL) on the internet. If the server has no internet connection, this will result in the MMC being basically unusable. To fix this, CRL checking can be unchecked in the Internet Settings (intetcpl.cpl):

References:

https://support.citrix.com/article/CTX139325

If you have the misfortune of having to troubleshoot and repair boot issues on a virtual machine after a physical host crash, these two commands might help you.

First of all, try to get into the advanced settings on boot (it should be the F11 key), or after a while Windows (Server or 10/11) might automatically go into the menu when it cannot boot from disk. Alternatively a Windows ISO image can be used.

Once in the advanced settings, run the good old checkdisk command:

chkdsk /f C:

After completion, restart the VM and check if you are able to boot. If the issue persists, try restoring the registry database (once again through the advanced settings or a Windows ISO). A scheduled task regularly backs up the registry and puts it the folder C:\Windows\System32\config\Regbak.

copy C:\windows\system32\config\RegBack\* C:\windows\system32\config

Restart the VM and check if you are able to boot into Windows. If you still have issues, you should consider restoring from a backup (it sucks but sometimes it is unavoidable).

In an Active Directory environment, it is best practice to enable DNS Aging and Scavenging. Aging and Scavenging will ensure that old DNS entries (such as decommissioned servers or computers) are deleted regularly. You will find this option by opening the properties in DNS Manager under the advanced tab or in the properties of a Forward Lookup Zone.

For detailed information, check out https://www.windowstechno.com/dns-aging-and-scavenging/.

If you are having performance issues with your brand new File Server running on Windows Server 2019, particularly when working with small files over a network share, these PowerShell commands might save hours of troubleshooting.

Get-NetAdapter | Set-NetAdapterAdvancedProperty -DisplayName “Large Send Offload Version 2 (IPv4)” -DisplayValue “Disabled” -NoRestart

Get-NetAdapter | Set-NetAdapterAdvancedProperty -DisplayName “Large Send Offload Version 2 (IPv6)” -DisplayValue “Disabled” -NoRestart

Get-NetAdapter | Set-NetAdapterAdvancedProperty -DisplayName “Recv Segment Coalescing (IPv4)” -DisplayValue “Disabled” -NoRestart

Get-NetAdapter | Set-NetAdapterAdvancedProperty -DisplayName “Recv Segment Coalescing (IPv6)” -DisplayValue “Disabled” -NoRestart

Get-NetAdapter | Set-NetAdapterAdvancedProperty -DisplayName “Receive Side Scaling” -DisplayValue “Disabled” -NoRestart

Get-NetAdapter | Restart-NetAdapter

Note: The VM’s network adapter will be restarted, there will be a downtime of about 10 seconds.

References:

https://community.spiceworks.com/topic/2225989-server-2019-network-performance?page=8#entry-8745935