Chapter 7 Archiving Features in Exchange Online (part 2/2) Explained
How do you actually reach archived mail in Outlook, and how do you keep an eye on archive size without guessing? This part answers those two questions.
How do you actually reach archived mail in Outlook, and how do you keep an eye on archive size without guessing? This part answers those two questions. It shows where the archive lives in the desktop client, how to search it on purpose, and how admins can check usage with a few clicks or a short PowerShell command. The goal is simple: make sure every message, folder, and contact is still there when you need it.
Finding and using the archive in Outlook for desktop
When a user has an Exchange Online archive enabled, Outlook for desktop shows it as a second mailbox in the folder pane. The label is usually “Online Archive,” but an admin can set a custom name. It sits below the primary mailbox, with its own Inbox, Sent Items, and custom folders.
To open archived mail, launch Outlook and expand the Archive mailbox in the left pane. Click into any folder to read messages as usual. You can move items between the primary mailbox and the archive by dragging or using Move to Folder. This is helpful when you want to free up space in the main mailbox but keep older mail easy to reach.
Search works the same way, with one important detail. The search box in Outlook defaults to the current mailbox. If you want to search the archive, set the scope explicitly. In recent Outlook builds, click the search box, then choose “All Mailboxes” or “Online Archive” from the scope options. This prevents the common mistake of searching only the primary mailbox and concluding the message is missing.
A small example makes this clear. Suppose a user needs a vendor invoice from two years ago. The primary mailbox holds the last 12 months. The archive holds everything older. If the user searches with the scope set to “Current Mailbox,” Outlook returns nothing. Change the scope to “Online Archive,” run the same search, and the message appears. The message was never lost. The search just looked in the wrong place.
Monitoring archive mailbox usage and sizes
An archive that grows without notice can surprise you at renewal time or during a migration. Exchange Online gives two straightforward ways to check size and item count: the Exchange Admin Center and PowerShell.
In the Exchange Admin Center, select a user, open the Others tab, and choose “Manage mailbox archive.” The view shows the archive status and basic usage data. This is the fastest path for a single mailbox when you are already in the admin portal.
PowerShell gives you more control and a clean way to export results. For a single user, run:
Get-Mailbox -Identity "User email" -Archive | Get-MailboxStatistics | Select DisplayName,TotalItemSize,ItemCount
Replace “User email” with the user’s address or alias. The output shows the display name, total size, and number of items in the archive. This is enough to decide whether to adjust retention policies or plan a migration window.
To check all mailboxes with archives, use:
Get-Mailbox -Archive | Get-MailboxStatistics | Select-Object DisplayName,TotalItemSize,ItemCount
This returns a list for every archive-enabled mailbox. You can pipe the results to a CSV file for analysis in Excel or another tool. That export step matters when you manage many users. A spreadsheet lets you sort by size, spot outliers, and plan moves in batches instead of reacting to one full archive at a time.
Why this matters for migration and recovery
Archives are often the last piece people remember during a migration. The primary mailbox moves cleanly, but the archive is overlooked until someone asks for last year’s project mail. The steps above remove that risk. If you can see the archive in Outlook and measure its size in the admin tools, you can include it in your migration plan from the start.
The same logic applies to recovery. When a user reports missing mail, the first check is whether the message lives in the archive. A targeted search with the correct scope often finds it in seconds. If the archive is large, the size and item count help you decide whether to export it as a separate PST or move it as part of a full mailbox migration.
You now know where the archive appears in Outlook, how to search it on purpose, and how to monitor its size with admin tools or a short PowerShell command. That is enough to treat the archive as a first-class part of the mailbox, not an afterthought.
This piece fits the promise of The Migration Brief: one practical fix, one file format explained, and one safer way to move your mail. The fix here is setting the search scope to the archive. The format is the Exchange Online archive mailbox itself. The safer way to move mail is to measure and plan for the archive before the migration starts.