Stellar Merge Mailbox for Outlook: Combine Your PST Files Into One
Stellar Merge Mailbox for Outlook is a $39 one-year Windows program that combines several Outlook PST files into a single one, and can remove duplicates along the way. It's for people with years of archive PSTs scattered across drives, and the free version lets you check the merged result before you pay, with the sender and subject fields masked.
Every Outlook user who stays long enough ends up with archive.pst, backup-2019.pst and old-laptop.pst, and each one has to be opened and searched separately. Outlook has no merge button. You can import one PST into another by hand, but that gets slow, and it doesn't deal with duplicates. This tool does the combining in one pass and leaves the original files as they were.
Quick facts
- Version: 8.0.0.3, released December 2024
- Developer: Stellar Data Recovery (this product used to be called Stellar Merge PST)
- Runs on: 64-bit Windows 11, 10, 8.1, 8 and Windows Server 2012
- Works with: PST files from Outlook 2003 through 2024 and Office 365
- Needs: Microsoft Outlook installed
- Saves to: a new or existing PST, an Outlook profile, Office 365 or an Exchange server
- Price: $39 for 12 months at checkout
- Free version: previews the merged mail with From, To, Subject and similar fields showing "Demo"
- What we checked: the installer on Stellar's server (12.3 MB, file version 8.0.0.3), the trial limits and Outlook requirement in Stellar's manual and FAQ, the edition table on Stellar's buy page, and the $39 price and 12-month renewal on the order page on November 6, 2026. We didn't merge any PST files ourselves.
Before you buy
- Your PST files must be healthy. Stellar says this tool can't merge damaged or corrupt PST files, so repair them first.
- You must have Outlook installed. It can't join PST files without it.
- The current version dates from December 2024. That's older than Stellar's other tools, although it does list Outlook 2024 support.
- This is a yearly license. Merging PSTs is usually a one-time job, so turn auto-renewal off at checkout. Stellar's refund policy excludes renewals, and refuses buyers who didn't try the evaluation version first.
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Overview
You drag PST files onto the window, or find them with the search option, and tick the ones you want. You then choose between two ways of combining them. Merge folds matching folders together, so all the Inboxes become one Inbox. Join keeps each file's folders apart under its own root folder, which is safer if you want to know where each message came from.
Before starting, you can tick options to drop duplicates, the Deleted Items folder and the Junk folder. When it's done, the log report records which files and folders went in, and when.
The main window: drag PST files in, or use Add PST or Find PST on the ribbon.
Features
Merge or Join, your choice
Stellar Merge Mailbox for Outlook gives you two results from the same files. Merge combines the contents of matching folders. Join creates a separate root folder per source file inside one PST, keeping the hierarchy of each.
The merge screen: source folders on the left, items in the middle and saving options on the right.
Removes duplicates while merging
Stellar Merge Mailbox for Outlook can leave out duplicate items as it combines files. By default it compares a few fields, and you can tick advanced criteria such as sender name, recipient, internet header, attachments and date and time of sending. Overlapping backups are where this pays for itself.
The Home ribbon: options to exclude Deleted and Junk folders, and the duplicate criteria.
Merge only what you need
Stellar Merge Mailbox for Outlook can combine selected folders, such as Contacts or Calendar, rather than whole files. If you only want every old contact in one place, you don't have to bring along the mail as well.
Handles password-protected and archive PSTs
Stellar Merge Mailbox for Outlook merges password-protected PST files once you enter the password, and it works with archive files and PSTs from different Outlook profiles and versions.
Several places to save
Stellar Merge Mailbox for Outlook can write to a new PST, add to an existing PST, or send the result to an Outlook profile, Office 365 or an Exchange server. Stellar's manual says the original PST files aren't modified.
The same files set up to Join, with each PST keeping its own folder tree.
Real-World Uses
- Ten years of archives. Yearly archive PSTs go into one searchable file.
- Overlapping backups. Three backups of the same mailbox are combined, and the duplicates removed.
- Two mailboxes after a merger. An old company address and a new one end up in a single Outlook data file.
- Contacts cleanup. Only the Contacts folders from several PSTs are pulled together.
Who It's For, and Who Should Skip It
Buy it if you have several healthy PSTs, especially overlapping ones, and don't want to spend an evening in Outlook's Import wizard. It's a small and focused utility, and $39 is reasonable for it.
Skip it if you only have two small PSTs without overlap, because Outlook's own import will do that for free. Skip it if your files are damaged, since you'll need a repair tool like Stellar Repair for Outlook first. For merging Gmail, Yahoo or Thunderbird mailboxes rather than PST files, you need the $129 Technician edition, not this one.
Usage Guide
- Back up your PST files, and install the program on a Windows PC with Outlook.
- Drag your PSTs into the window, or click Add PST or Find PST, then click Next.
- On the ribbon, tick Remove Duplicate and any exclude options you want.
- Tick the folders you want, then choose Merge PST or Join PST under Saving Options.
- Choose where to save: a new PST, an existing PST, an Outlook profile, Office 365 or Exchange. Enter the password for any protected file.
- Check the preview in the free version, then activate your license and run the merge.
- Open the result in Outlook, and keep the log report.
Added PST files are listed with their size, dates and path before you continue.
Where it falls short
- No corrupt files. It stops at damaged PSTs. Stellar's answer is another Stellar product.
- The trial hides key fields. From, To, CC, BCC and Subject all read "Demo" in the preview, so you can check the mail body and attachments but not much else.
- Not much independent testing. We found no detailed hands-on review, so you're relying more than usual on your own trial.
- The Standard edition is PST-only. Online mailboxes and other formats are Technician features.
- Time depends on size. Stellar gives no speed figures, and large merges can take a while.
What Users Say
There isn't much to quote here. This is a niche utility, and we found no detailed independent review or a substantial group of Trustpilot reviews that name it. An honest short section is better than a padded one.
What we could find
Softpedia lists version 8.0.0.3 and gives it 5.0 out of 5 in a short editor's review, calling it a lightweight app.
Experts Exchange, quoted on Stellar's buy page: "It is a worthwhile purchase for IT Support technicians who tend to do a lot of repair work for Outlook users."
Trustpilot: Stellar as a company scored 4.8 out of 5 from 5,601 reviews when we looked, across all its products. The complaints there are mostly about refunds. unhappy consumer (November 18, 2025, 1 star): "Stellar software's refund policy is a trap."
Comparisons
Stellar Merge Mailbox vs Outlook's Import wizard
Outlook can import one PST into another at no cost, and it can skip duplicates in a basic way. It works on one file at a time and gives you no log. Stellar is worth paying for when you have many files, or big overlapping backups.
Editions and Pricing
| Edition | Price | License | What it adds |
|---|
| Standard (this listing) | $39 at checkout ($39.99 on Stellar's site) | 12 months | Merges and joins PST files, removes duplicates |
| Technician | $129 on Stellar's site | 12 months | Merges online mailboxes such as Microsoft 365, Gmail and Yahoo, plus DBX, NSF and 20+ mail clients |
| Toolkit | $199 on Stellar's site | 12 months | Adds PST repair, OST conversion, splitting, compacting, undelete and password recovery |
FAQs
Can Stellar Merge Mailbox for Outlook merge just the Contacts folders?
Stellar Merge Mailbox for Outlook can merge specific folders from several PSTs, including Contacts, Calendars, Tasks and Journals, without merging everything else.
Does Stellar Merge Mailbox for Outlook change my original PST files?
Stellar Merge Mailbox for Outlook creates the merged data without modifying the originals, according to its manual. Back them up anyway if they're important.
Can Stellar Merge Mailbox for Outlook merge a corrupt PST file?
Stellar Merge Mailbox for Outlook can't merge damaged or corrupt PST files. Repair them first with a tool like Stellar Repair for Outlook, then merge.
Is there a size limit in Stellar Merge Mailbox for Outlook?
Stellar Merge Mailbox for Outlook has no stated file size limit. Stellar says it handles PSTs of any size, and the time taken depends on how large they are.
Which Outlook versions does Stellar Merge Mailbox for Outlook support?
Stellar Merge Mailbox for Outlook supports PST files from Outlook 2003 through 2024 and Office 365, according to its manual.
Is this the same as Stellar Merge PST?
Stellar Merge Mailbox for Outlook is the current name of Stellar Merge PST, and it has moved on from version 6 to version 8.
System Requirements
- 64-bit Windows 11, 10, 8.1, 8 or Windows Server 2012
- Intel-compatible x64 processor
- 4 GB of RAM (8 GB recommended)
- 250 MB of disk space for installation, plus room for the merged PST
- Microsoft Outlook installed
Conclusion
Stellar Merge Mailbox for Outlook is worth $39 if you have several healthy PST files, and especially overlapping backups, to turn into one. The one reason to buy it is the duplicate removal, which Outlook's own import handles only in a basic way.
The main reason not to buy is that two small PSTs don't need it, and that there's little independent evidence for how it copes with very large files. Try the free preview on your own PSTs first, and turn auto-renewal off at checkout.
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