Auto Archiving in Outlook: How to Set It Up, and What Replaced It
Auto archiving in Outlook moves older email out of your main mailbox automatically. In classic Outlook for Windows, AutoArchive moves it to a .pst file on your computer (File > Options > Advanced > AutoArchive Settings). New Outlook doesn't have AutoArchive. On Microsoft 365, the online archive does the same job in the cloud.
"Outlook says my mailbox is full. Also, I can't find anything from 2019." That's one of the most common calls in IT, and it's usually one problem wearing two hats. Somebody turned on auto archiving years ago, it quietly shipped half their email to a file on their laptop, and nobody has thought about it since. Including the laptop.
TL;DR: Classic Outlook's AutoArchive still works, but it saves old mail to a local .pst file that's easy to lose and usually isn't backed up. New Outlook and Outlook on the web don't have AutoArchive at all. For a Microsoft 365 business, turn on the online archive instead. It moves old mail automatically, stays in the cloud, shows up on every device, and Business Premium gives each user up to 1.5 TB of archive space.
What Is Archiving in Outlook? Three Features, One Name
Microsoft uses the word "archive" for three different things, which explains a lot of confused tickets.
The Archive button and folder. One click moves an email out of your inbox into a folder called Archive. It's still in the same mailbox. It's tidying, not storage.
AutoArchive (classic Outlook only). Moves older items on a schedule into a separate .pst file, usually on your computer.
Online archive (Microsoft 365). A second mailbox in the cloud, attached to yours. Old mail moves there automatically based on policies your admin sets.
Microsoft's AutoArchive support page describes the goal: "Keep your Outlook inbox and its folders under control by moving older items you want to keep to an archive." The real question is which archive.
How to Set Up Auto Archiving in Outlook (Classic)
On classic Outlook for Windows, here's how to turn on AutoArchive:
Click File > Options > Advanced.
Under AutoArchive, click AutoArchive Settings.
Check Run AutoArchive every [n] days and pick a schedule.
Set Clean out items older than to the age you want.
Choose Move old items to and note the file location. That's your archive .pst.
Click Apply these settings to all folders now, then OK.
You can also set rules per folder. Right-click the folder, choose Properties, and open the AutoArchive tab.
Microsoft's AutoArchive settings explained page lists the default aging periods:
Inbox and Drafts: 6 months
Sent Items and Deleted Items: 2 months
Outbox: 3 months
Calendar, Tasks, Notes, and Journal: 6 months
One setting to watch: Permanently delete old items. It does exactly what it says. Pick it, and AutoArchive stops archiving and starts deleting. It does not mean "tidy up," no matter how tired you are when you click it.
Why New Outlook Doesn't Have AutoArchive
If you switched to new Outlook for Windows and can't find AutoArchive, you're not missing a menu. Microsoft says it straight: "AutoArchive feature is not available in new Outlook for Windows."
New Outlook is built around cloud mailboxes, like Outlook on the web. It can open .pst files, but Microsoft's .pst guide notes that "Opening .pst files in new Outlook requires classic Outlook to also be installed." That's like a new car that only plays CDs if you keep the old car in the garage.
Your options in new Outlook, Outlook on the web, and Outlook for Mac:
Use the online archive. Best for Microsoft 365 businesses. More below.
Archive by hand with the Archive button, or set up a rule that files messages into folders.
Keep classic Outlook if you rely on AutoArchive. Microsoft's new Outlook availability guide says classic Outlook support continues "until at least 2029."
Where Do Archived Outlook Emails Go?
Depends which archive grabbed them. Check three places:
The Archive folder in your folder list. That's where the Archive button sends things.
Online Archive or In-Place Archive, a separate mailbox listed below your main one. That's the Microsoft 365 archive.
Archives, a separate data file in classic Outlook. That's the AutoArchive .pst. The AutoArchive Settings window shows the exact file path.
In classic Outlook, change the search scope to All Mailboxes or All Outlook Items to search everything at once. As Microsoft notes, "By default, when you use classic Outlook's search tools, Outlook only searches the current mailbox."
The Online Archive: Auto Archiving for Microsoft 365
This is the part most how-to guides skip, and it's the one I'd actually set up for a business.
According to Microsoft's archive mailbox documentation, once the archive is on, "a user's current mailbox becomes their primary mailbox and an additional and associated mailbox is created, called the archive mailbox."
Two things then move mail into it on their own:
The default retention policy, which "Moves items that are two years or older from a user's primary mailbox to their archive mailbox."
Threshold-based auto-archiving, which moves the oldest items "when mailbox usage exceeds a safe threshold, which is 96% of the mailbox quota by default."
Space depends on your license. Per Microsoft's Exchange Online limits, mailboxes on Business Basic, Standard, and Premium are 100 GB. The archive is 50 GB on Basic and Standard. On Business Premium it starts at 100 GB and auto-expands to 1.5 TB. (If you fill 1.5 TB with email, I have questions. Mostly about reply-all.)
The online archive works in classic Outlook, new Outlook, the web, and mobile. Microsoft treats it as part of the user's mailbox for search, retention, and litigation hold. And it isn't sitting on a laptop one coffee spill away from history.
Does Archiving Emails Free Up Space in Outlook?
Archive button: No. The mail moves to another folder in the same mailbox. Same size.
AutoArchive to .pst: Yes, for your mailbox on the server, because the mail moves into a file on your PC. It uses your computer's disk instead.
Online archive: Yes, for your primary mailbox. The archive has its own separate quota.
PST Files Are Where Old Email Goes to Get Lost
My honest take after 20 years: for a business, a .pst file on a laptop is the riskiest place to keep email.
It's usually not backed up. Microsoft 365 backup tools cover mailboxes, not a file in someone's Documents folder.
It lives on one device. Laptop dies, gets stolen, or gets replaced, and the archive goes with it unless someone remembers to copy it.
It can get corrupted. Microsoft ships a repair tool, ScanPST, for a reason.
It has a ceiling. Microsoft's .pst size limit article puts the default at 50 GB.
It walks out the door. A .pst file copies to a USB drive as easily as a vacation photo.
If you're cleaning up an old classic Outlook setup, import the .pst files into each user's online archive and retire them. Our guide to managed backup and disaster recovery covers why mailbox backups matter too.
AutoArchive Not Working? Restart Outlook First
My most repeated advice in IT is also the least exciting: restart it first. A big share of "it stopped working" calls end with closing the app and opening it again. AutoArchive is no exception.
If a restart doesn't fix it, check these:
You're on new Outlook. AutoArchive doesn't exist there.
Outlook has to be running. AutoArchive works while classic Outlook is open. A laptop that sleeps all weekend archives nothing.
The folder is excluded. Check the folder's Properties > AutoArchive tab.
Your account doesn't allow it. Microsoft notes "Archive and AutoArchive might not be available if your mail profile connects to an Exchange Server," often because the company uses an online archive policy instead.
The .pst file is full or damaged. Run ScanPST, or point AutoArchive at a new file.
The "Mailbox Full" Call Is Usually a Five-Minute Fix
A lot of "everything's broken" calls turn out to be something small. A full mailbox is a classic. Email stops sending, panic spreads, and the fix is turning on the online archive, letting the policy move the oldest mail, and emptying Deleted Items. Five minutes, start to finish.
It still counts as a call, and that's fine. A flat rate isn't a meter for how long the fix takes. It pays for someone picking up the phone and knowing which of the three archives to check.
The Archive Setup I'd Recommend for a Small Business
If you asked me to set up email archiving for a 10 to 50 person office on Microsoft 365, here's the list:
Turn on the online archive for every user.
Keep the default two-year move policy unless you have a reason to change it.
Leave threshold auto-archiving on, so nobody hits a full mailbox.
Import old .pst files into each user's online archive, then delete the local copies.
Stop new .pst files with Group Policy or Intune, so they don't creep back.
Set a retention policy that matches your legal and industry requirements, so old email gets deleted on purpose instead of by accident.
Back up Microsoft 365, archive included. Microsoft keeps the service running. Keeping your data recoverable is still your job.
When You Don't Need Us for This
One to five people on classic Outlook who want a tidier inbox: AutoArchive works fine. Just back up the .pst file.
A Microsoft 365 admin comfortable in the admin center: turning on the online archive takes a few clicks.
Get help if you have years of .pst files scattered across laptops, a legal hold or retention requirement, or someone whose entire email history lives on a laptop older than your newest hire.
Straight Answers About Auto Archiving in Outlook
How do I auto archive in Outlook?
In classic Outlook, go to File > Options > Advanced > AutoArchive Settings and turn on Run AutoArchive. In new Outlook or Outlook on the web, use the Microsoft 365 online archive, which your admin turns on.
Where do archived emails go in Outlook?
To the Archive folder, the Online Archive mailbox, or a local .pst file, depending on which feature moved them. Search All Mailboxes to check them all.
Does archiving emails free up space in Outlook?
The Archive button doesn't. AutoArchive to a .pst file and the Microsoft 365 online archive both free space in your main mailbox.
Why is AutoArchive missing in Outlook?
You're probably using new Outlook, Outlook on the web, or Outlook for Mac. AutoArchive only exists in classic Outlook for Windows.
What is the difference between Archive and AutoArchive?
Archive moves selected emails into an Archive folder in the same mailbox. AutoArchive moves old items on a schedule into a separate .pst file.
Can I turn off auto archiving in Outlook?
Yes. In classic Outlook, clear the Run AutoArchive checkbox. The online archive policy is controlled by your Microsoft 365 admin.
Mailbox Full Again? Give Us a Call
If your email is scattered across .pst files, Archive folders, and a laptop nobody dares turn off, give us a call at 410-703-3857 or send us a note. Our IT help desk sorts out Outlook for businesses across Maryland, Virginia, and DC, including Columbia, at one flat monthly rate.
We'll find your email from 2019. We can't promise you'll want to read it.
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