---
title: Outlook Archiving Didn’t Reduce Email Storage (IMAP Accounts)
description: "## Outlook Archiving Didn’t Reduce Email Storage (IMAP Accounts) If you use **Outlook Classic** with an **IMAP** email account and enable archiving (for example, “archive anything older than 6 months”), you may notice that your **mailbox storage usage does not decrease**. This is expected behaviour…"
url: "https://www.domaincentral.com.au/help/outlook-archiving-didnt-reduce-email-storage-imap/"
updated: "2026-08-20"
category: Email
---

# Outlook Archiving Didn’t Reduce Email Storage (IMAP Accounts)

## Outlook Archiving Didn’t Reduce Email Storage (IMAP Accounts)

If you use **Outlook Classic** with an **IMAP** email account and enable archiving (for example, “archive anything older than 6 months”), you may notice that your **mailbox storage usage does not decrease**.

This is expected behaviour for IMAP. In most cases, **nothing is broken** — it’s a common misunderstanding of how IMAP works.

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### Why Archiving Doesn’t Reduce IMAP Mailbox Size

With **IMAP** accounts:

- Your email is stored on the **mail server**.
- Outlook is a **sync client** that displays what is on the server.
- Outlook’s **Archive / AutoArchive** feature typically saves a copy to a **local archive file (PST)**.
- **The original messages usually remain on the server** unless they are moved out of the IMAP mailbox or deleted.

**Result:** Your Inbox/Sent folders on the server still contain the same email, so **server mailbox storage stays the same**.

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### Important: “Archiving” vs “Reducing Storage”

- **Archiving for organisation** (moving messages into an IMAP “Archive” folder that still sits under the IMAP account) will **NOT** reduce storage usage — the email is still stored on the server.
- **Reducing storage usage** requires messages to be **moved to a local (non-IMAP) location** or **deleted from the server**.

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### How to Actually Reduce IMAP Mailbox Storage

#### Option A (Recommended): Move Old Mail to a Local Outlook Archive (PST)

This stores old mail on the computer in an Outlook data file (PST), and removes it from the server.

1. Open **Outlook Classic**.
2. Go to **File** → **Account Settings** → **Account Settings**.
3. Open the **Data Files** tab and confirm you have an **Outlook Data File (.pst)** listed.
   - If you do not have one, click **Add…** and create a new PST file (e.g. *Archive.pst*).
4. In your Outlook folder list, locate **Outlook Data File** (this is **local**, not the IMAP account).
5. Create an archive folder under the PST (example: **Archive 2024**).
6. Select older emails in your IMAP folders (Inbox/Sent/etc.) and **drag them into the PST archive folder**.
7. Allow Outlook time to sync changes.

**Tip:** Mail moved into folders under **Outlook Data File** is stored locally and will no longer count toward your server mailbox quota.

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#### Option B: Archive Locally, Then Delete from the Server

If Outlook has already created an archive file but storage hasn’t changed, Outlook may have archived a copy but **did not remove the original messages** from the IMAP mailbox.

1. Confirm your archive exists: **File** → **Account Settings** → **Data Files**.
2. Verify the old emails are present in your archive/PST.
3. Delete the same old emails from the IMAP folders (Inbox/Sent/etc.).
4. Empty **Deleted Items** (this is important).
5. Wait for Outlook to finish syncing.

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### Common Reasons Storage Still Doesn’t Drop

- **Emails were moved into an IMAP “Archive” folder** (still stored on the server).
- **Deleted Items is not emptied** (messages still count until purged).
- **Sent Items** and other folders contain most of the mail (not just Inbox).
- **Large attachments** are the main cause of mailbox usage.
- Outlook hasn’t finished syncing changes yet (especially on large mailboxes).

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### Recommended Best Practice

- Use IMAP for day-to-day email across multiple devices.
- If you need to reduce mailbox size, move older email into a **local PST archive**.
- **Back up your PST file** — it is stored on the local computer and is not automatically protected by the mail server.

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### Need Help?

If you’re unsure whether your archived mail is stored **locally** or still on the **server**, contact support and let us know:

- Whether the account is configured as **IMAP**
- Which Outlook version you are using (**Outlook Classic** / **New Outlook**)
- Approximately how large the mailbox is currently using

We can help confirm the safest way to archive mail without losing anything important.