Ceyhun KIRMIZITAS

26Oct 2026 by Ceyhun Kirmizitas 0 Comments

Exchange Server NLS Sort Version Mismatch in a Mixed Windows Server DAG: ESE 643, 613, and ExchangeStoreDB 124

Exchange, Exchange Server SE / 2019 / 2016, Migration & Upgrade

Applies to: Exchange Server SE / 2019 ESE Event IDs 643 and 613, together with ExchangeStoreDB Event ID 124, were recorded when copies of the same Exchange mailbox database ran on DAG members using different Windows Server sorting versions. The issue is not limited to an in-place upgrade. The investigation began with a production Exchange Server 2019 DAG. New Exchange Server Subscription Edition (SE) servers running Windows Server 2022 had been added to that DAG, and copies of the existing mailbox databases had been created on the new servers. ESE Event ID 613 and ExchangeStoreDB Event ID 124 were reported. I reproduced the error pattern in a separate Exchange environment, including the NLS sort version mismatch reported by ESE Event ID 643. I examined two scenarios: adding new Exchange SE…

25Oct 2026 by Ceyhun Kirmizitas 0 Comments

Windows Server DHCP Failover in Hot Standby Mode: Address Allocation, Recovery, and Lease Lifecycle

Windows Server

Applies To: Windows Server 2025 / 2022 / 2019 / 2016 Windows Server DHCP Failover in Hot Standby mode uses an active server and a standby server to maintain availability. When the active server becomes unavailable, how many IP addresses can the standby assign to new clients, and when do those addresses become available? The questions behind this article came from a customer engagement. In environments serving hundreds of thousands or even millions of DHCP clients across many scopes, exact standby capacity and failover timing matter when planning for outages and deciding whether existing settings need adjustment. For example, during an active-server outage, new clients can fail to get an address even though the scope still shows thousands of free addresses. In Windows Server 2022 lab, I used two DHCP…

18Oct 2026 by Ceyhun Kirmizitas 0 Comments

Field Guide: Exchange Server SE Hybrid Modern Authentication with All Mailboxes On-Premises

Exchange, Exchange Server SE / 2019 / 2016, Hybrid

Applies to: Exchange Server SE / 2019* / 2016* *See Section 1.1 for version-specific HMA compatibility and minimum Exchange Server CU and HU/SU requirements. Organizations may need to keep all their Exchange mailboxes on-premises for business, technical, or regulatory reasons, but still want to enable Modern Authentication and use Microsoft Entra ID features such as MFA. Hybrid Modern Authentication (HMA) makes this possible without moving mailboxes to Exchange Online. Supported Exchange clients can authenticate through Microsoft Entra ID while their mailboxes remain on-premises. In this Field Guide, I show how I configured HMA on Exchange Server SE using Microsoft Entra Connect, the Hybrid Configuration Wizard (HCW), and Exchange PowerShell. The configuration covers Classic Outlook, OWA, and ECP, with both Password Hash Synchronization (PHS) and Pass-through Authentication (PTA). The guide also…

17Oct 2026 by Ceyhun Kirmizitas 0 Comments

Field Guide: Kerberos Authentication in Exchange Server – Configuration and Validation

Exchange, Exchange Server SE / 2019 / 2016, Security & Hardening

Applies to: Exchange Server SE / 2019 / 2016 Microsoft is moving away from NTLM in Windows. For Exchange Server administrators, this raises an important question: What does this mean for Exchange client authentication, and where does Kerberos fit in? In discussions with customers, I sometimes get the impression that moving away from NTLM means everything in Exchange should use Kerberos. But that is not how Exchange works. Different clients and services use different authentication methods. Kerberos can help reduce NTLM dependency, but it cannot replace all of them. So I wanted to focus on three practical questions: Where does Kerberos really fit in Exchange Server? What does it take to configure it correctly? And how can we confirm that clients are actually using Kerberos rather than falling back to…

11Oct 2026 by Ceyhun Kirmizitas 0 Comments

Exchange Server and Teams Calendar Integration Without HCW

Exchange Server SE / 2019 / 2016, Microsoft Teams

Applies to: Exchange Server SE / 2019 | Microsoft Teams Microsoft Teams Calendar can be integrated with Exchange Server on-premises. Normally, we use the Hybrid Configuration Wizard (HCW) to configure the integration between Exchange Server and Microsoft 365. However, some customers keep all their mailboxes on-premises, with no mailboxes in Exchange Online. They use Microsoft Teams but do not need mailbox migration, hybrid mail flow, or other Exchange coexistence features. HCW can also configure additional Hybrid components, such as Organization Relationships, IntraOrganizationConnectors, and mail flow connectors, depending on the selected options. For this scenario, I wanted a more controlled approach. Instead of running HCW, I wanted to configure only the components required for Teams Calendar and understand what each one does. I started with basic Teams Calendar integration and then…

04Oct 2026 by Ceyhun Kirmizitas 0 Comments

Manage Exchange Server Transport Log Paths with ExchangeLogPathManager.ps1

Exchange Server SE / 2019 / 2016

Applies to: Exchange Server SE / 2019 / 2016 Exchange Server can generate a large amount of log data over time, especially Message Tracking, SMTP protocol, and connectivity logs. By default, these logs are usually stored under the Exchange installation path, which is commonly on the system drive. I created ExchangeLogPathManager.ps1 to make it easier to review and compare transport log paths across multiple Exchange servers, and safely move supported high-growth transport logs to a dedicated log drive when needed. The script works with supported Transport Service, Front End Transport, and Mailbox Transport log path settings. Version 1.1 also adds Interactive Configure and explicit Review modes while keeping the same Preview, confirmation, pre-change snapshot, drift protection, Apply, and verification workflow. Download ExchangeLogPathManager.ps1 Download from GitHub Questions and feedback are welcome…

02Oct 2026 by Ceyhun Kirmizitas 0 Comments

Manage Exchange Server URLs and Namespaces with ExchangeURLManager.ps1

Exchange Server SE / 2019 / 2016

Applies to: Exchange Server SE / 2019 / 2016 Configuring Exchange Server Client Access URLs is rarely a one-time task. The URLs are set after a new installation, checked again during migrations, changed when a server is replaced or the namespace design changes, and compared when a new server needs to match the existing ones. The Exchange commands themselves are not complicated. The harder part is everything around those commands: checking the current configuration, deciding what should be carried over, seeing exactly what will change, keeping a backup, and verifying the result afterward. That was the main reason I created ExchangeURLManager.ps1. The goal was not only to set Exchange URLs. I wanted one tool that could review the current configuration, compare Exchange servers, configure namespaces, clone the required settings, create…

27Sep 2026 by Ceyhun Kirmizitas 0 Comments

Exchange Server SE Readiness Check Before Installation

Exchange Server SE / 2019 / 2016

Applies to: Exchange Server SE RTM | Windows Server 2025 / 2022 / 2019 Over the years, I have seen many Exchange Server installations take longer than expected because of Windows Server, Active Directory, DNS, network, storage, or prerequisite problems. Even when Exchange Setup completes successfully, configuration differences can still cause unexpected behavior afterward. In some cases, recommended settings may also need to be reviewed and applied later. Many of these issues can be identified before Exchange Setup starts. That was the idea behind ExchangeServerReadinessCheck.ps1. I first created these checks for my own Exchange upgrade and migration work. Later, I added more checks based on different environments and real cases. This can be especially useful for Field Engineers, Consultants, and administrators who perform Exchange deployments, upgrades, or migrations periodically and…

23Sep 2026 by Ceyhun Kirmizitas 0 Comments

Windows 11 25H2 to 26H2 Upgrade: First Impressions

Windows 11, Windows Client

Applies to: Windows 11 26H2; upgrade from Windows 11 25H2 On September 23, 2026, Windows 11 version 26H2 appeared in Windows Update on my Windows 11 Enterprise laptop. I decided to upgrade from Windows 11 25H2, OS Build 26200.9448, to 26H2 and document the process. After the upgrade, I also checked some of the newer Windows features to see what had actually changed and how they worked in daily use. This article is based on my experience with Windows 11 Enterprise. Some features or options may be different on other editions or device configurations, and Windows features can change with future updates. I may update this article as I continue using 26H2. In This Article 1. Upgrading from Windows 11 25H2 to 26H2 2. Upgrade Experience 3. Taskbar Position and…