Looking to free up space and speed up Outlook? Learn how to auto archive in Outlook (2025) using the best Outlook Auto Archive settings. This simple, step-by-step guide shows how to automatically archive emails, reduce mailbox size, and keep your inbox organized with ease.

Managing an overflowing mailbox can slow Outlook down, cause search delays, sync failures, and even block new incoming emails — especially when using Microsoft Exchange, Outlook.com (15 GB free mailbox), or enterprise accounts with storage quotas. Auto Archive is one of Outlook’s most effective built-in features for long-term mailbox management. It keeps your primary mailbox lean, improves performance, and preserves years of important email history without forcing you to delete anything.

This comprehensive guide walks through Outlook 365, Outlook 2024/2021/2019/2016, classic Outlook, Outlook for the web, and mobile apps, covering exactly how Auto Archive works, where archived data goes, and how to fix issues when AutoArchive is missing or not running.

What Is Auto Archive in Outlook & Why You Should Use It

Auto Archive is an automated cleanup feature in the classic Outlook for Windows app. It periodically moves older emails, calendar entries, notes, tasks, and other Outlook items into a local Outlook Data File (.pst).

This reduces mailbox size, improves search responsiveness, and helps meet retention or compliance needs.

Practical benefits of enabling Auto Archive

Benefit	Why it matters
Reduces mailbox size	Prevents “Mailbox Full” errors and improves sync with Exchange/Outlook.com.
Boosts Outlook performance	Smaller mailboxes load, index, and search faster.
Supports compliance	Helps meet company/industry requirements for long-term data retention.
Improves backup times	Smaller active mailbox = faster backups and restores.
Organizes historical mail	Keeps your inbox tidy while letting you access old emails anytime.

When to pick Auto Archive vs other options: choose Auto Archive (classic) to free server mailbox quota by moving items to a local .pst. If you need cross-device access or your organization uses an Online Archive (server-side), prefer the server mailbox approach described later.

Outlook Archive vs Auto Archive: Key Differences You Must Know

Outlook includes two different archiving approaches — they behave very differently and users often confuse them.

Archive Button (Manual Archive): quick tidy

Moves selected messages to the built-in Archive folder inside your mailbox (server/cloud).
Does not reduce mailbox size — good for decluttering only.
Available on Windows, Mac, Web, and Mobile.

Auto Archive (Automatic PST Archiving): frees space

Moves older items into a local .pst file (archive.pst).
Reduces mailbox size because items leave the server mailbox.
Only available in the classic Outlook desktop app (not in the new Outlook or most web clients).

Online Archive (Enterprise): server-side vault

For Microsoft 365 business accounts: an archive mailbox lives on the server and can be auto-moved by admin policies.
Frees primary mailbox quota and remains searchable across devices (subject to admin policy and retention rules). For very large archives, Microsoft supports auto-expanding archiving.

Quick reference — where archived mail goes

Archive (button): Archive folder inside mailbox (no quota relief).

AutoArchive: archive.pst on your local drive (frees mailbox space).

Online Archive: server archive mailbox (frees primary mailbox and is managed centrally).

How Outlook Auto Archive Works: Aging Periods, PST Files & Storage Rules

How Outlook decides when items are archived

Outlook looks at age. Which date counts depends on item type and your settings:

Email: received date or last modified date (unless you set the registry tweak to ignore last modified).

Calendar: last saved date (the scheduled date for events).

Tasks: completion date (open tasks aren’t auto-archived).

Notes: last modified date.

Contacts: not auto-archived by default.

Pro tip: If you regularly edit or move old messages (which updates the modified date), Outlook may delay archiving those items. Use the ArchiveIgnoreLastModifiedTime registry key to force archiving by received date (instructions later).

Default aging periods

Inbox, Drafts, Calendar, Tasks, Notes > 6 months
Sent Items, Deleted Items > 2 months
Outbox > 3 months

You can change these per folder or globally in AutoArchive settings.

PST / OST size limits

Modern Outlook (2013 > Outlook 365 / 2024): default PST limit 50 GB. Increasing it via registry is possible but not recommended — large PSTs raise corruption and performance risks.

Why size matters: when a PST reaches its limit Outlook may stop archiving or behave unpredictably. Best practice: split archives (yearly PSTs), compact files, or use server-side archives for very large histories.

How to Set Up Auto Archive in Outlook (Classic App): Step-by-Step Guide

Important: AutoArchive is a classic desktop feature. If you’re in the new Outlook for Windows or using Outlook on the web, follow the rule-based instructions in Section 6.

Open AutoArchive settings

File > Options > Advanced
Click AutoArchive Settings.

This opens a dialog with all controls: schedule, prompt, delete vs. move, aging, and PST location.

Configure schedule and behavior

Run AutoArchive every N days: set a cadence (1–99). Frequent runs avoid large one-time moves.

Prompt before AutoArchive runs: useful if you want a heads-up (untick for silent operation).

Delete expired items (email folders only): cleans items explicitly expired via message options.

Archive or delete old items: must be checked to enable the lower options.

Show archive folder in folder list: shows the archives as a mailbox in the folder pane.

4.3 Choose aging and storage

Clean out items older than: pick days/weeks/months.
Move old items to: browse to choose or create an archive .pst (default path shown below).
Permanently delete items: only when you want deletion instead of archiving — use with caution.

Default archive location: C:\Users\<username>\Documents\Outlook Files\archive.pst (newer Outlook). Older setups may use %localappdata%\Microsoft\Outlook\archive.pst. You can change this path to store multiple year-based PSTs.

Folder-specific AutoArchive

Right-click any folder
Select Properties > AutoArchive tab.

Options let you override global settings: exclude a folder, set a custom age, or delete older items automatically. Great for Sent Items vs Inbox differences.

Apply or disable

Apply these settings to all folders now — applies the current configuration globally.
To turn off AutoArchive, uncheck Run AutoArchive every N days in the AutoArchive dialog.

How to Run Auto Archive Manually (Clean Up Old Items Tool)

When you need instant space reclamation (mailbox full or prepping a migration):

File > Info > Tools > Clean Up Old Items
Choose Archive this folder and all subfolders or Archive all folders according to their AutoArchive settings
Set the Archive items older than date and an archive file path (or accept default)
Click OK

Why use this: manual archiving lets you split archives (e.g., create individual PSTs per year), include items marked Do Not AutoArchive, and run a one-time cleanup before backup or migration.

How to Auto Archive Emails in Outlook 365 Using Rules (When AutoArchive Is Missing)

If AutoArchive is greyed out or not present (common in new Outlook), create a Rules and Alerts rule that moves older messages to a folder or archive mailbox.

Create an archiving rule

File > Options > Mail > Rules and Alerts
New Rule > Start from a blank rule > Apply rule on messages I receive
Choose condition where the message is older than X days (set X)
Action: move it to the specified folder (choose your Archive folder)
Add exceptions (e.g., high importance, specific senders)
Name and enable the rule

Limitations to note:

This simulates archiving but only frees server quota if the destination is a separate Online Archive mailbox or is stored server-side. If it moves to a folder inside the same mailbox, mailbox size won’t shrink.
For complex or scheduled server-side archiving, consider admin-managed retention policies or Power Automate flows for cloud automation.

Reminder: new Outlook uses different automation features; verify whether Sweep or other mailbox rules are moving messages automatically if you see unexpected behavior.

How to Manually Archive Emails in Outlook (Windows, Mac, Web, Mobile)

Manual archiving is supported across platforms — useful for quick cleanup.

Windows

Select email(s) > press Backspace, or click Archive on the ribbon, or drag to the Archive folder.

Mac

Use Control + E, right-click > Archive, or use the ribbon button.

Outlook on the web

Select messages > click Archive. There’s no classic AutoArchive; instead use rules or Sweep.

iOS / Android

Swipe to Archive, or multi-select then Archive icon.

Important: Archiving this way usually does not reduce mailbox server quota — it typically moves messages into the mailbox’s Archive folder unless your org uses server-side archiving.

Best Folder Structure for Outlook Archive & Long-Term Inbox Management

A thoughtful folder structure ensures archived mail stays organized and easy to retrieve years later.

Recommended structure

Top-level year folders: Archive – 2025, Archive – 2024

Sub-folders by project/client: Archive – 2024 / Project X

Limit nesting to 2–3 levels to keep paths short and searches fast

Use consistent naming conventions (YYYY – Dept – Topic)

Consider quarterly splits for very large volume (Q1/Q2/Q3/Q4)

Why this helps: Smaller PSTs per year are easier to back up, compact, and restore. They also reduce corruption risk vs one enormous PST.

How to Manage PST Files for Outlook Auto Archive (Storage, Limits & Backups)

Proper PST management prevents data loss and keeps Outlook stable.

Backup strategy

Regularly copy closed PST files to a secure backup (external drive or enterprise backup).
Keep at least one offsite or cloud backup for disaster recovery.

Compacting PST

File > Account Settings > Data Files > Settings > Compact Now
Compacting reclaims space after large deletes or moves.

Avoid network/cloud sync for PSTs

Storing a PST on OneDrive / Dropbox / network shares can cause corruption. Keep PSTs local.

When PST gets large

Create a new yearly PST and move older items into it.
If a PST is damaged, run Inbox Repair Tool (ScanPST.exe) — its typical location is inside the Office installation folder (e.g., C:\Program Files (x86)\Microsoft Office\root\Office16).

Outlook Auto Archive Not Working? Troubleshooting & Quick Fixes

Symptoms & fixes

AutoArchive greyed out

Your admin disabled it or you have an Online Archive enabled (Exchange policy), or you’re in the new Outlook client (no AutoArchive). Check with your IT admin.

AutoArchive not running

Ensure Run AutoArchive every N days is checked.
Check folder-level Do not AutoArchive settings.
If PST is corrupt, run ScanPST.exe to repair.

Items not archived

Item’s modified date may be more recent than the aging setting. Use the ArchiveIgnoreLastModifiedTime registry tweak to archive by received date if needed — be careful and back up the registry first.

Archive mailbox not visible

Enable Show archive folder in folder list or manually Open Outlook Data File (File > Open & Export > Open Outlook Data File).

PST reached size limit

Move older data into a new PST, compact, or split by year. Default modern limit is 50 GB — avoid exceeding it.

Outlook Auto Archive FAQ

Does Outlook Auto Archive delete emails?

Only if you pick Permanently delete old items in AutoArchive settings. Otherwise, items are moved to an archive .pst file.

Why is my AutoArchive setting missing?

Either you’re using the new Outlook (feature unavailable) or your admin has disabled AutoArchive via policy or Exchange Online Archive is active.

Where can I find my archived emails?

Built-in Archive folder in your mailbox (Archive button)
Open the .pst via Open Outlook Data File for AutoArchive files (archive.pst) — default path: C:\Users\<user>\Documents\Outlook Files\archive.pst.

How often does AutoArchive run?

You decide — set it to run every 1–99 days, or run Clean Up Old Items manually.

Can I Auto Archive only the Inbox?

Yes — set per-folder AutoArchive settings via: Right-click Folder > Properties > AutoArchive.

Extra Tips, Advanced Options & Alternatives

Registry: archive by received date

If you want Outlook to ignore the last modified time and archive strictly by received date, create the

ArchiveIgnoreLastModifiedTime DWORD under: \HKEY_CURRENT_USER\Software\Microsoft\Office\<version>\Outlook\Preferences and set it to 1.

Back up the registry first and check with IT if you’re in a corporate environment.

Auto-expanding archiving (enterprise)

Microsoft 365 offers auto-expanding archiving for very large archive mailboxes (server side). This keeps archived data on the server and expands storage automatically up to organizational limits — useful for legal/long-term retention. Check your admin settings for availability.

When to use server policies vs local PSTs

Use server-side (Online Archive/retention policies) for compliance, discovery, and cross-device access.
Use local PSTs when you need offline long-term storage and want to reduce server quota quickly (remember backup, security, and corruption risks).

Power Automate option

If new Outlook lacks AutoArchive and you need cloud automation, consider Power Automate flows to move older messages into a separate mailbox or SharePoint/OneDrive (design with security and retention in mind).

Conclusion: Keep Outlook Fast by Automating Email Archiving

Auto Archive is an effective tool for maintaining a healthy mailbox — keep your primary mailbox lean, speed up search and backups, and organize years of messages safely. Use the classic AutoArchive for local PST-based archiving, rules and Online Archive for server-side management, and follow the PST best practices above to avoid corruption or performance problems.

Official Microsoft Support & Documentation

AutoArchive Settings Explained (Microsoft Support) – Detailed explanation of how AutoArchive works, when it runs, and how items are moved to an archive location.
Archive Older Items Automatically (Microsoft Support) – Step-by-step instructions on setting up auto archive in Outlook Desktop.
Enable Archive Mailboxes for Microsoft 365 (Microsoft Docs) – How admins can enable server-side Online Archive mailboxes for Microsoft 365.
How to Enable Archiving in Outlook (Microsoft Q&A) – Community Q&A confirming the steps to manually archive and enable AutoArchive in classic Outlook.
Archive Items Manually (Microsoft Support) – Instructions for manual archive using Clean Up Old Items, including options to include/exclude “Do Not AutoArchive” items.
Checking AutoArchive Settings (Microsoft Q&A) – Quick rundown of where to find and review AutoArchive settings in Outlook Desktop and Outlook Web.

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How to Auto Archive in Outlook (2025): Best Outlook Auto Archive Settings Explained