Corbett

Office 365 Backup Tool

Corbett Office 365 Backup Software copies a Microsoft 365 mailbox to your own disk as PST, MBOX, EML, MSG, PDF, HTML, CSV or TXT. You sign in on Microsoft's own page, with two-step verification if your account uses it. The folder tree, attachments and timestamps ride along with the mail. Windows only.

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4.6 out of 5 from 683 reviews

Your mailbox is read on your own machine. Nothing is uploaded to a Corbett server.

Free demo, verified clean by VirusTotal and 30 days to claim your money back.

Lifetime licence from $99 Free trial saves 10 emails per folder

Microsoft 365 specifics

What Office 365 Backup Copies Over

Office 365 Backup Tool reads one Exchange Online mailbox at a time over the same connection Outlook uses and writes an offline copy to your disk. Microsoft 365, Office 365 and O365 are the same mailbox under three names. An account holds more than a mailbox, so the list of what is left behind matters as much as the list of what arrives.

Comes across

  • All mail folders
  • Attachments
  • Inline images
  • Message dates
  • Read status
  • Full headers
  • Contacts
  • Calendar

Folders read

  • Inbox
  • Sent Items
  • Drafts
  • Archive folder
  • Deleted Items
  • Junk Email
  • Custom folders

Saves as

Not included

  • Online Archive
  • Shared mailboxes
  • Public folders
  • OneDrive
  • SharePoint
  • Teams chats
  • Mailbox rules
  • Account settings

The Archive folder and the Online Archive are two different things

The Archive folder sits inside the mailbox and is backed up like any other folder. The Online Archive is a second mailbox that Microsoft attaches to some plans. It is not reachable the way the main mailbox is, so it stays on the server.

Office 365 mailbox to PST

Core features

Office 365 Backup, Screen by Screen

Five screens, in the order an Office 365 mailbox backup runs from sign-in to the written file.

Adding a Microsoft 365 account in Office 365 Backup Tool

Connect

Microsoft 365 Sign-In With MFA

Pick Office 365 from the list and the server details fill themselves in. A Microsoft sign-in window opens, you enter your address and password there, approve the two-step prompt if your account has one and the mailbox loads. The credential stays on Microsoft's side and out of the program.

  • Host and port resolved for you
  • Two-step verification, also called MFA, works as normal
  • No admin rights needed to back up your own mailbox
  • No app password to generate, Microsoft 365 mail has no app password route
  • Several mailboxes queued in one run, each with its own sign-in
Mailbox folder tree with checkboxes

Folder selection

Pick Which Folders to Back Up

The mailbox opens as a folder tree with a checkbox on every branch and a message count beside it. A single project folder can be saved on its own. Deleted Items and Junk Email can be left out with one click each.

  • A checkbox on every folder and subfolder
  • Message counts shown before anything is written
  • Subfolder structure kept in the output
  • Empty folders hidden with the compact view
Message preview with hex and raw views

Message preview

Read a Mailbox Before Exporting

Each message opens in a preview pane with four analysis views beside it. IT staff copying a mailbox for a legal request use the header and raw views to confirm what they are about to share.

  • Content shows body, sender, recipient and subject
  • Message header exposes routing and delivery hops
  • Properties lists size, priority and attachments
  • Hex and raw message give the full source
Filter options for a selective backup

Selective backup

Back Up a Single Quarter of Mail

Filters are applied before the run starts. Everything a departing employee exchanged with one client in one financial year is saved on its own, which is the shape most Microsoft 365 backup requests take.

  • Date range with a From and a To
  • Sender, recipient, subject or message content
  • Only messages that carry an attachment
  • Message size, to leave large mail out
  • Skip junk or duplicate messages
Backup format and destination options

Output options

Save the Backup to Disk or Mailbox

You choose where it goes at the very end. The output can be a file in a local folder, on an external drive or on a mapped network share, or it can be piped straight into a second live account. Document output follows a naming rule, so a folder holding thousands of files stays ordered and easy to search.

  • Mail formats: PST for Outlook, MBOX for Thunderbird or Apple Mail, EML, MSG
  • Document formats: PDF, HTML, CSV, TXT
  • Straight into Google Workspace, another Microsoft 365 account or any IMAP host with the email migration software
  • PST output opens in any Outlook edition and imports back into Microsoft 365
  • Attachments, email addresses and phone numbers pulled out on their own
  • Each run is a full copy of the folders you ticked. There is no scheduler, so a repeat backup is started by hand

Putting a saved PST back into a mailbox later is the email recovery software, the restore half of the same download.

Before you connect

Signing In to a Microsoft 365 Mailbox

Microsoft changed the rules for third party software in 2022 and many guides were never updated. Three points to settle before adding a mailbox.

Changed

Your password alone no longer works

Microsoft switched off password based sign-in for mail software in October 2022. Any program that asks you to type a Microsoft 365 password into its own form will be refused. Office 365 Backup Tool opens Microsoft's sign-in window instead and receives a token, not your password. Microsoft brands the method modern authentication.

Not needed

There is no app password

Gmail and Yahoo hand out app passwords for outside software. Microsoft 365 mail has no such route. If a guide tells you to create one, it is describing a different provider. An authenticator app, a text code or a security key all appear in the usual Microsoft prompt.

No

One admin sign-in does not cover the tenant

It works mailbox by mailbox. Each account is added with its own sign-in, then all of them run together. An administrator who needs every mailbox in the organization without each user present should use Content Search in Microsoft Purview, covered below.

If the sign-in window closes with an error, the account may be blocked from signing in or a conditional access policy may be limiting which applications can connect. Both are set by the administrator, not by Office 365 Backup Tool.

Free demo

Try it on one mailbox first

Install it, sign in on Microsoft's page, tick a folder and pick a format. Nothing is written to disk until you begin the run.

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Why a copy

How Long Microsoft 365 Keeps Mail

Microsoft keeps the service running. Keeping the data is your responsibility, and that split is written into its shared responsibility model. A copy on a disk that is not connected to the account also stays untouched if ransomware or a compromised sign-in empties the mailbox. These are the windows that matter.

14 days

A message removed from Deleted Items

It moves to the Recoverable Items folder and stays there for 14 days by default. An administrator can raise that to 30 days at most. After that it is gone unless a retention policy or hold was already in place.

30 days

A mailbox whose licence is removed

When a user leaves and the licence is taken away, Exchange Online holds the mailbox for 30 days. Then it is deleted and no administrator or support ticket can bring it back. Most requests for Office 365 Backup Tool start with that 30 day limit.

Paid add-on

Microsoft 365 Backup restores, it does not export

Microsoft's own backup service costs $0.15 per GB per month and restores mail back into Microsoft 365. It does not give you a file on your own disk. A local PST or PDF on a disk you control is a different thing, and that is what a Microsoft 365 backup tool such as Corbett writes.

Mailbox size is capped by plan, 50 GB on Business plans and 100 GB on E3 and E5. A full mailbox rejects new mail. Moving old years to a local file is the usual way to keep the account under the cap.

Before you buy

Outlook Export vs Office 365 Backup

If Outlook is already installed, it can write your own mailbox to a PST at no cost. That handles a single account in a single format. The table marks where it runs out.

Task Outlook export Office 365 Backup Tool
Cost Free with Outlook $99 one time
Your own mailbox, once, to PST Built for exactly that Also does it, but you are paying for the rest
Which Outlook Classic Outlook. New Outlook exports mail only Outlook not needed at all
Output format PST only Eight formats including PDF and MBOX
Date, sender or subject filter Not in the export wizard Applied before the run
Several mailboxes One account per export, one export at a time Queued together in one run
Waiting on a sync first Yes, the whole mailbox must download into Outlook No, it reads the server directly
Headers and raw source Not shown during export Full preview before anything is written

Rows tinted green are the ones where Outlook wins.

One account, PST only and classic Outlook already installed: use Outlook and skip the purchase. Administrators who need many mailboxes without each user present have Content Search in Microsoft Purview, which needs the eDiscovery Manager role and produces export packages that expire after 14 days. Both routes are walked through in our Office 365 mailbox to PST guide.

Specifications

What Office 365 Backup Needs to Run

Download details

Released
Dec 2020
Download size
87.4 MB
Trial limit
10 emails per folder
Delivery
Download link and key by email
Licence
Lifetime, up to 5 machines
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System

Hard disk
150 MB to install, plus room for output
RAM
4 GB minimum
Processor
1 GHz, 2.4 GHz advised
Rights
Run as Administrator
Outlook
Not required

Supported editions

Runs on Windows 11 through 7, either 32 or 64 bit. Windows Server editions from 2008 through 2025.

No macOS or Linux build.

Building Windows email utilities since 2020. The people who answer support tickets are the people who write the code.

Working process

See an Office 365 Mailbox Saved

Prefer text? The written guide shows the same run as screenshots.

Office 365 backup walkthrough

Common questions

Common Office 365 Backup Queries

Signing in, what is copied and where Office 365 Backup Tool stops.

Does Microsoft not back up Microsoft 365 already?

Microsoft keeps the service available. It does not keep a copy of your mail for you, and its shared responsibility model says so. A deleted message is held for 14 days by default, a mailbox with no licence for 30 days. After those windows the data is gone. A file on your own disk is the only copy nothing else controls.

Why does Office 365 Backup Tool open a Microsoft sign-in window?

Because Microsoft stopped accepting passwords typed into third party software in October 2022. It sends you to Microsoft's own page, you sign in there and it receives a token that lets it read the mailbox. The program never handles the password itself.

Does Office 365 Backup Tool work with two-step verification?

Yes. Because sign-in runs on Microsoft's page, any authenticator, text code or security key shows up just as it does in a browser. Nothing has to be turned off and no app password is involved, since Microsoft 365 mail has no app password route.

Can an admin back up every Microsoft 365 mailbox at once?

No. One mailbox is added per sign-in. Several can be queued and run together, but each needs its own sign-in. For the whole organization without each user present, Content Search in Microsoft Purview is the route and it needs the eDiscovery Manager role.

Does the Microsoft 365 backup include the Online Archive?

No. The Online Archive is a separate mailbox that Microsoft attaches to certain plans and it is not exposed the way the main mailbox is. The Archive folder inside the mailbox is different and is backed up like any other folder.

Can a Microsoft 365 shared mailbox be backed up?

A shared mailbox has no sign-in of its own, so it cannot be added directly. If the administrator has assigned it a licence and enabled sign-in, it behaves like a user mailbox and can be added. Otherwise Content Search is the route for shared mailboxes.

PST or PDF for a Microsoft 365 mailbox backup?

PST when the mail may go back into Outlook or another Microsoft 365 account later. PDF when the copy is for a person who does not have Outlook, or for a legal or HR file that must be readable in ten years. Many people write both, since the run can be repeated with a different format.

Does the backup include Microsoft 365 contacts and calendar?

Yes, when the mailbox carries them. Contacts export to a vCard file and calendar items to an ICS file beside the saved mail. Teams chats, OneDrive files and SharePoint libraries are separate services and stay where they are.

Does a backup free space in the Microsoft 365 mailbox?

Not by itself. Reading is one way only, so the server copy is left exactly as it was. Once you have opened the local copy and checked it, delete the old folders in Outlook yourself to bring the account back under its 50 GB or 100 GB cap.

Is there a Microsoft 365 mailbox size limit?

No. The licensed edition puts no cap on mailbox size or message count. A large mailbox takes longer because Exchange Online limits how fast a client may read, but nothing stops before the end. A dropped link does not restart the run; it picks up from the last saved message.

Can the Microsoft 365 mailbox of an employee who has left be backed up?

Yes, as long as the mailbox still exists and someone can sign in to it. Do it before the licence is removed, or within 30 days of removal. After that the mailbox is deleted and there is nothing left to copy.

Does Microsoft 365 mail pass through Corbett's servers?

No. It runs on your machine and connects from there to Microsoft. The output lands on the disk or drive you pick. Corbett stores nothing and relays nothing.

Does Office 365 Backup Tool run on Mac or Linux?

No. Office 365 Backup Tool is a Windows application only, from Windows 7 through Windows 11 and Windows Server 2008 through 2025. There is no macOS or Linux build.

What does the free Office 365 backup demo include?

It signs in to any Microsoft 365 account, loads every folder and gives you the full preview and all the filters needed to backup Office 365 mailbox data. The backup itself stops at 10 emails from each folder, which is enough to open the output and confirm it looks the way you expect.

Step by step

Office 365 Walkthroughs and Guides

Each guide below covers one task in full, from the first click to the saved file.

Getting the mail out

Moving to another host

Opening the result

Other providers are covered on the email backup software page. Moving a Microsoft 365 account into another account is the email migration tool. Converting a finished file to another format is the email converter software. Reading a saved file without writing anything is the free email viewer software. Apple Mail users have the iCloud backup tool. A Google Workspace domain uses the Google Workspace backup tool. Shared hosting mail has the Webmail backup tool. Sibling pages: Gmail backup tool, Outlook.com backup tool, Hotmail backup tool and Yahoo backup tool.

User testimonials

What Office 365 Admins Report

Across 683 reviews of the backup and restore wizard.

4.6 out of 5

Collected across 683 reviews from software directories and direct customer feedback. The three examples below are verbatim.

Saved O365 mailboxes locally

Awesome tool. I bought Office 365 backup wizard full version to save my O365 mailboxes locally for future use. The software has performed really well, and saved all data without any error.

Samantha Roth

Microsoft 365 mail to IMAP

I wanted to move my Office 365 mails to my IMAP account. After looking on the internet for a while, I came upon this tool and, it really helped me to achieve the archive process.

Steven Frew

Office 365 backup to hard drive

My Manager asked me to secure all mails to hard drive. But manual backup is very time-taking process. So, I decided to go with Office 365 email backup tool which helped me to download the emails easily.

Dave Adams

Get started

Keep an Office 365 Backup Before the Licence Goes

Download the demo, sign in on Microsoft's page and save 10 emails from every folder at no cost. Personal licence $99 one time, with 30 day money back.

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87.4 MB · Windows 11 to 7 and Windows Server 2025 to 2008 · 30 day money back