Reduce Your Mailbox Size (Before You Can't Send or Receive Email)

ℹ️ Mailboxes fill up — usually because nothing ever gets deleted — and once yours gets full, email stops working. First you lose the ability to send, then you lose the ability to receive. This article explains the limit, what happens as you approach it, and the fastest ways to free up space. The good news: the first three steps below fix it for almost everyone.

🛑 The 50 GB Limit Is Fixed — Please Don't Ask Us to Raise It

Every mailbox has a hard ceiling of 50 GB. This is a Microsoft limit on our plan, and it cannot be raised — not by Argus IT, not by anyone. Please don't submit a ticket asking for more space, because the answer can only be no.

What we can help with is reducing what's in your mailbox, and using your archive (more on that below). But the 50 GB ceiling itself is fixed.

⚠️ What Happens as Your Mailbox Fills Up

Email doesn't just stop all at once. It fails in stages — and the nasty part is the last stage, where you may not even realize anything is wrong.

⚠️ That last stage is the dangerous one. Once you're full, guests, coworkers, and vendors emailing you get a bounce-back, and you have no idea they tried. Don't wait for the warning at 49 GB to become a crisis — clean up regularly.

✅ The Fastest Ways to Free Up Space

Do these in order. The first three handle the vast majority of cases.

1. Delete your largest emails (biggest win by far)

Almost all of your mailbox size comes from a small number of emails with large attachments — photos, videos, PDFs, presentations. Find and delete those and you'll recover space fast.

• In Outlook, sort a folder by size (click the column heading, or use the sort/arrange options) so the biggest emails come to the top.
• Or use search to find large items — search for size:>5 MB (or size:huge) to surface the big ones.
• Delete the large emails you no longer need. If you need to keep an attachment, save it to OneDrive or the file server first, then delete the email.

2. Empty your Deleted Items and Junk folders

Here's what trips people up: deleting an email just moves it to Deleted Items — it still counts against your limit until you empty that folder.

• Right-click the Deleted Items folder → Empty Folder.
• Do the same for the Junk Email folder.

If you've been "deleting" mail for years but never emptying Deleted Items, this step alone can recover a lot.

3. Clean out your Sent Items

People forget that Sent Items counts toward your total too. Every large attachment you've ever sent is still sitting in there.

• Open Sent Items, sort by size, and delete the old ones with big attachments.

🧰 The Storage Tool — Your Cleanup Hub (New Outlook)

The quickest way to see where your space is going — and clear out the worst folders in bulk — is the Storage page. The company is moving everyone to new Outlook, so this is the version to learn.

💡 Which Outlook do I have? New Outlook has a "New Outlook" toggle in the top-right corner of the window. If it's on (or you're using Outlook in a web browser at outlook.com), you have new Outlook and the steps below apply. (If you're still on classic Outlook, the equivalent is File → Tools → Mailbox Cleanup — but most staff are now on new Outlook.)

Step 1: Open the Storage page

1. Click the Settings (⚙️ gear) icon in the top-right corner of Outlook.
2. In the settings window, go to Accounts → Storage.
3. If you have more than one account, choose the right one from the dropdown at the top.

Step 2: See where your space is going

Under Manage Storage, you'll see a folder-by-folder breakdown — exactly how much space your Inbox, Sent Items, Deleted Items, and every other folder is using.

This is the most useful part: instead of guessing, you can see at a glance which folders are the problem. For most people the biggest culprits are the Inbox, Sent Items, and Deleted Items.

Step 3: Clear out a folder in bulk

Next to each folder there's an Empty option. Click it and you'll be able to delete either:

• All emails in that folder, or
• Only emails older than 3, 6, or 12 months.

The "older than" option is the safe and powerful one. It lets you clear years of old mail out of a big folder in a single action while keeping everything recent. For example, emptying everything in your Inbox older than 12 months can recover a large amount of space at once without touching this year's email.

⚠️ Bulk deletion is serious — look before you leap. Deleted mail goes to Deleted Items first (and then to a short-term recovery area), but don't bulk-empty a folder unless you're confident you don't need what's in it. If you want to keep the mail, use the Online Archive instead (see the next section) — it moves mail out of your mailbox without deleting anything.

Bonus: Sweep (for newsletters and repeat senders)

New Outlook also has Sweep, handy if a single sender (a newsletter, an automated report, a noisy distribution list) is filling your mailbox. Select a message from that sender, click Sweep, and you can do things like "delete everything from this sender older than 10 days" or "keep only the latest" — and have it apply automatically going forward.

📦 The Long-Term Fix: Use Your Online Archive

If you're someone who genuinely needs to keep years of email, deleting isn't the answer — archiving is.

Your account may have an Online Archive — a separate storage area that does not count against your 50 GB mailbox limit. It shows up in Outlook's folder list (usually near the bottom) as "Online Archive – [Your Name]" or "In-Place Archive."

• Drag old emails into the Online Archive. They're still fully searchable and accessible — they just no longer count against your main mailbox.
• This is the best solution for people who don't want to delete anything: you keep everything, but your main mailbox stays healthy.

💡 Don't see an Online Archive in your folder list? Submit a ticket and we'll tell you whether your account has one, or enable it if appropriate.

⚠️ A note on old "AutoArchive to a PST file" advice: older guidance tells you to archive to a local PST file on your computer. We don't recommend this — PST files live only on your computer, aren't backed up, and are easily lost if your computer fails. Use the cloud Online Archive instead.

🧹 Make It a Habit

The reason mailboxes fill up is simple: nothing ever gets deleted. A few minutes of regular upkeep prevents the whole problem:

• Delete emails you don't need as you go, rather than letting them pile up.
• Empty Deleted Items every so often (it doesn't free space until you do).
• Watch for large attachments — save the ones worth keeping elsewhere, and delete the email.
• Check the Storage page now and then (Settings ⚙️ → Accounts → Storage) to see how full you're getting and clear out old mail before it becomes a problem.

🔧 A Note on "Advanced" Fixes (Leave These to IT)

You may come across advice involving registry edits, OST file size limits, or disabling Cached Exchange Mode. Two honest points about those:

1. Those settings are about Outlook's local cache file on your PC — not your mailbox size on the server. They don't fix the "can't send/receive" problem, which is about server mailbox size.
2. Some of them (especially registry changes) can break Outlook if done wrong.

Please don't attempt registry edits. If your Outlook is slow or your local cache is causing problems, submit a ticket and IT will handle it properly.

🆘 When to Submit a Ticket

Submit a ticket if:

• You've cleaned up using the steps above and you're still near the limit and not sure what else to remove.
• You want to know whether you have an Online Archive, or need one enabled.
• You've already lost the ability to send or receive and need help getting back under the limit quickly.
• Outlook is running slowly and you suspect a local cache (OST) problem.

ℹ️ What we can't do: raise your mailbox above 50 GB. That limit is fixed by Microsoft and applies to everyone — so the fix is always to reduce what's stored or move it to the archive.

Related Articles

• Access Your Email Online (KB# 130004)
• Add Company Email to Your Phone (KB-130005)
• The Basics to Try When You Have a Problem (KB# 10001)
• How to Fill Out a Ticket (KB# 10002)

ArgusIT KB# 130007 | Original: July 30, 2025 (Vincent Kruggel) | Rebuilt: May 25, 2026

Tags: mailbox, mailbox full, mailbox size, unable to send mail, cannot send email, cannot receive email, 50gb, archive, outlook full, quota