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--- software:microsoft:outlook [2025/01/08 20:13] – superwizard
+++ software:microsoft:outlook [2026/08/15 04:30] (current) – superwizard
@@ Line 1: / Line 1: @@
+====== Outlook Desktop ======
+-------------------------------------------------------------------------------------------------------------------------------------------------\\
+====== Outlook database repair ======
+<WRAP center round box >
+This is what i did:
+  * Check if these are .OST vs. .PST Files
+    * If these clients are using Microsoft 365, Exchange, or IMAP, their local file is an .OST (Offline Storage) file, not a .PST file. If that is the case, you do not need to deal with local file corruption at all:
+    * **Adjust the Sync Slider**: Go to Account Settings > Account Settings > Change Account and move the "Mail to keep offline" slider down from "All" to 1 Year or 6 Months.
+    * Delete the .OST: Close Outlook and delete the bloated .ost file. Outlook will automatically rebuild a clean, lightweight 10–15 GB OST file containing recent mail, while the rest of their 100 GB historical archive remains safely accessible in the cloud.
+</WRAP>
+You are hitting one of the most infamous brick walls in Windows desktop IT.
+You are entirely right about SCANPST.exe (the built-in Inbox Repair Tool). It was designed decades ago for PST files measured in megabytes, not 100 gigabytes. When a database crosses 50 GB, SCANPST usually enters an endless scanning loop, drops corrupted items silently, or claims it "repaired" the file while leaving the underlying B-tree indexing broken.
+Even though the Windows Registry override (MaxFileSize / MaxLargeFileSize) allows Outlook to grow past 50 GB, Outlook’s legacy database engine simply isn't engineered for that level of continuous I/O. At 50 GB to 100 GB+, single-bit flips, disk fragmentation, or a sudden shutdown will cause immediate, recurring corruption.
+You don't have to blow away the data and start over. Here is how to fix these databases and permanently end the corruption loop.
+  * Ditch SCANPST for Third-Party Extraction Tools
+    * When SCANPST.exe fails, professional IT admins use specialized PST recovery tools. These tools do not try to fix the corrupted 100 GB file in place. Instead, they bypass Outlook's indexing, scrape the raw data sectors from the file, and extract the healthy items out into brand-new, uncorrupted PST files.
+    * The industry standards for handling heavily corrupted >50 GB PSTs include:
+    * Stellar Repair for Outlook (or Stellar Toolkit): Excellent at parsing massive, oversized files and rebuilding clean folder structures. Crucially, it has a built-in feature to "Split PST while saving" into 10 GB or 20 GB chunks.
+    * Kernel for Outlook PST Repair: Very reliable for deep block-level corruption on bloated enterprise PSTs.
+    * DataNumen Outlook Repair: Uses a very aggressive raw-recovery engine built specifically for worst-case, unreadable data files.
+    * Pro-Tip: Always copy the corrupted file to a fast local NVMe SSD before running these tools. Never attempt to repair or extract a 100 GB PST over a network share or inside a OneDrive synced folder.
+  * Re-architect the Files: The Multi-PST Strategy
+    * Once you extract the data, do not put it back into a single 100 GB file. Outlook handles multiple PST files linked in the sidebar effortlessly, but struggles with one giant file.
+    * Split by Year: Divide the user’s mail into separate archives (e.g., Archive_2020-2022.pst, Archive_2023-2024.pst, and an active Current.pst).
+    * Mount Them Simultaneously: Open all the smaller PST files in the client's Outlook profile (via File > Open & Export > Open Outlook Data File).
+    * Result: The client still sees all 100 GB of their historical email organized in their left sidebar, but Outlook is reading 5x 20 GB files instead of 1x 100 GB file. This completely eliminates the underlying database engine crashes.
+Enable Online Archiving: If they are on M365, enable In-Place Archiving on their account so old emails automatically move to an online archive mailbox instead of bloating local disk space.
+Recommended Emergency Triage Workflow
+Make a backup copy of the corrupted file right now.
+Run a trial/demo scan using an industrial recovery tool (like Stellar or Kernel) to verify it can read the tree structure.
+Export/Extract the recovered data out into 15 GB chunks.
+Attach those smaller PST chunks to a fresh Outlook profile.
+Are these oversized files local .PST archives (POP3/manual archives), or are they cached .OST files synced to a Microsoft 365 or Exchange server?
+====== To archive emails older than a specified date in Outlook ======
+you can use the Clean up old items feature or set up AutoArchive:
+Clean up old items
+   Select File > Info > Tools > Clean up old items
+   Select Archive this folder and all subfolders
+   Choose the folder to archive
 ====== Increase storage capacity of PST for Outlook 2003, 2007, 2010, 2013 and 2016 ======
@@ Line 22: / Line 86: @@
 You may modify the following UNICODE Registry values to increase the limits:
-The MaxLargeFileSize registry entry. The MaxFileSize registry entry determines the absolute
+Note: IF the PST key doesn’t exist under Outlook key, you have to create it manually.
-maximum
+Right-click on the right pane and from the menu that appears, choose:New >DWORD Value
+The
+   MaxLargeFileSize
+registry entry determines the absolute maximum
 size that both the .pst and the .ost files can grow to. After this maximum size is reached,
 Outlook does not permit the size of the file to grow beyond this size.
-The WarnLargeFileSize registry entry. The WarnFileSize registry entry determines the maximum
+The
+   WarnLargeFileSize
+registry entry determines the maximum
 data that both the .pst and the .ost files can have. After this maximum data is reached,
 neither the .pst nor the .ost files are permitted to add any more data. However, the size of
@@ Line 38: / Line 113: @@
 GB = 204800 X 95% = 194560 for Outlook 2010, 2013 and 2016.
 </code>
 </WRAP>