Corbett

Office 365 Backup Tool

Corbett Office 365 Backup Tool exports a Microsoft 365 mailbox to a local disk. Sign-in happens on Microsoft's own page, with MFA where the account uses it. Folder tree, attachments and timestamps come along. Output formats include PST, MBOX, EML, MSG, PDF, HTML, CSV and TXT. Windows only.

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4.6 out of 5 from 683 reviews

Microsoft 365 mail downloads to your PC only. Nothing goes to a Corbett server.

Free demo, scanned clean on VirusTotal and a 30-day money-back window.

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

Microsoft 365 coverage

Office 365 Backup Tool for Mail, Contacts and Calendar

Corbett Office 365 Backup Tool Saves Microsoft 365 Mail to Your PC

A removed licence deletes the mailbox 30 days later. Corbett Office 365 Backup Tool copies one Exchange Online mailbox at a time over the same connection Outlook uses and saves an offline copy.

Comes across

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

Folders backed up

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

Saves as

PST
MBOX
EML
MSG
PDF
HTML
CSV
TXT
vCard
ICS

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 like the main mailbox, so it stays on the server.

Office 365 mailbox to PST

Related backup pages: Outlook.com backup tool, Hotmail backup tool, Gmail backup tool, Google Workspace backup tool and Yahoo backup tool. Any other IMAP account is on the email backup software page.

Quick answer

What Is Office 365 Backup Tool?

Office 365 Backup Tool is a Windows program that exports a Microsoft 365 mailbox to a local disk. Sign-in happens on Microsoft's own page, with MFA where the account uses it, so your password stays with Microsoft.

What it saves

Microsoft 365 mail, attachments, contacts and calendar

Where it saves

A folder, an external drive, a network share or another live inbox

Who uses it

IT admins, leavers' managers and mailbox owners

Core features

Office 365 Backup Tool Features in Five Screens

Five screens of the Microsoft 365 backup tool, from sign-in to the saved file.

Microsoft 365 sign-in screen with MFA prompt

Connect

Microsoft 365 Sign-In With MFA

Select Office 365 from the list and server details fill in on their own. A Microsoft sign-in window opens for the address and password. Approve the two-step prompt if the account has one and the mailbox loads.

The credential stays on Microsoft's side. No admin rights are needed to back up a personal work mailbox, and no app password is needed. Several mailboxes can be queued, all with their own sign-in.

Office 365 folder tree with message counts and checkboxes

Folder selection

Select Office 365 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 drop out with one click apiece. Subfolder structure is kept in the output and compact view hides empty folders.

Message preview

Preview Office 365 Emails Before Export

Every 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 share.

Content opens body, sender, recipients and subject, message header maps the servers the mail passed through, properties sum up size, priority and file names, and hex with raw message print the untouched MIME source.

Office 365 filters by date, sender and size

Selective backup

Back Up a Leaver Mailbox by Date or Sender

Filters are applied before the backup starts. Everything a departing employee exchanged with one client in one financial year is saved on its own.

Date range with From and To dates, sender, recipient, subject or message content, only messages with an attachment, size to leave large mail out, and skip junk or duplicates.

Office 365 output format and destination options

Output options

Save Office 365 Mail to Disk or Mailbox

Select the destination at the end: a local folder, an external drive, a mapped network share or straight into a second live account. Naming rules keep thousands of files ordered and searchable.

PST for Outlook, MBOX for Thunderbird or Apple Mail, EML, MSG, plus PDF, HTML, CSV and TXT. Send mail into Google Workspace or another Microsoft 365 account with the email migration tool.

Flexible use

Three Ways to Back Up Office 365 With One Tool

One mailbox, a queue of mailboxes or a move to another account: Office 365 Backup Tool handles all three. Test your job in free demo before you buy.

Back up one leaver mailbox

Queue several mailboxes

Add every mailbox with its own sign-in, then process the queue in one go. Every mailbox gets a separate file.

Move mail to another account

Name Google Workspace, another Microsoft 365 account or an IMAP host as the target.

Before connecting

Microsoft 365 Login Through Entra ID

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

A password alone no longer works

Microsoft switched off password based sign-in for mail software in October 2022. Office 365 Backup Tool opens Microsoft's sign-in window and receives a token, not the password. Microsoft brands the method modern authentication.

Not needed

There is no app password

Microsoft 365 business mail never offered an app password route, so any guide that says to create one is about another provider. Authenticator, SMS codes and FIDO2 security keys all show up in the normal Microsoft prompt.

One by one

One admin sign-in does not cover the tenant

It works mailbox by mailbox. Every account is added with its own sign-in, then all of them process together. For every mailbox without every user present, use Content Search in Microsoft Purview.

A login window that shuts with an error means the user is blocked from signing in, or a Conditional Access policy in Entra ID limits which apps may connect. Both settings belong to the tenant admin, not to the backup tool.

Working process

How to Back Up Office 365 Emails in Four Simple Steps

Follow four steps to get a Microsoft 365 mailbox onto your drive. Practice on one folder in free demo.

Install Office 365 Backup Tool, choose Office 365 and sign in on Microsoft's window. Approve the MFA prompt if asked.

Select folders and filters

The mailbox opens as a tree with counts. Tick the folders to save, then limit by date, sender, attachment or size.

Select format and location

Choose PST, MBOX, EML, MSG, PDF, HTML, CSV or TXT, then point the tool at a folder, a drive or a network share.

Start Office 365 backup

Press Export and track every folder on the progress screen. A log and a CSV report list all saved mail.

Want screenshots for every click? Follow IMAP backup guide.

Working process

Office 365 Backup Tool Video Demo

Rather follow screenshots? IMAP backup guide shows an Microsoft 365 mail backup click by click.

Office 365 backup tool video walkthrough showing folder selection and backup progress

Advanced options

More Office 365 Backup Features for IT Admins

Small options that save hours on a leaver mailbox.

Microsoft sign-in window

Authenticator, SMS and security key supported

No app password

None exists for Microsoft 365 mail

Several mailboxes queued

One separate file per mailbox

Counts per folder

A tally beside every folder

Date range filter

Frame the backup with From and To dates

Sender and text search

Look up by sender, recipient, subject or words

Attachment filter

Only mail with files attached

Size limit

Leave large messages behind

Duplicates dropped

Skip junk and repeated copies

Resume on drop

A broken connection resumes, not restarts

Folder, drive or share

Save to a folder, external drive or network share

Log and CSV report

Proof of what was saved

Choose output

Office 365 Backup Formats and Where They Open

Eight output formats are on offer. Match the format to what you plan to do with the saved mail.

Format	Best for	Opens in
PST	Outlook users and mail that may return to an account	Microsoft Outlook
MBOX	Moving mail to a free email client	Thunderbird and Apple Mail
EML	One file per email, easy to search	Windows Mail and most email clients
MSG	Single messages kept as Outlook items	Microsoft Outlook
PDF	Printing and reading without Outlook	Any PDF viewer
HTML	Reading mail with no email client	Any web browser
CSV	Lists of senders, dates and subjects	Excel and Google Sheets
TXT	Plain text archives of old messages	Any text editor

Free demo

See Office 365 Backup Tool Work on One Mailbox

Install the demo, sign in on the Microsoft page, tick one folder and choose a format. Files appear only after the backup starts.

Download free demo

Try before you buy

Free Demo vs Full Office 365 Backup Tool

Free demo signs in on the Microsoft page, shows every folder, applies every filter and previews mail. Only saving is capped.

Feature	Free demo	Full version
Microsoft sign-in and folder list	Yes	Yes
Preview, filter and analysis views	All available	All available
Emails saved per folder	10	Unlimited
Mailbox size limit	Saving stops at 10 per folder	None
Price	Free	$99 one time
Machines per licence	Not applicable	Up to 5
Money back window	Not applicable	30 days

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Use cases

Microsoft 365 Mail Retention and Backup Limits

Microsoft keeps the service running. Keeping the data falls on the customer, and that split is written into its shared responsibility model.

14 days after a delete

A message removed from Deleted Items moves to Recoverable Items and stays 14 days by default. An administrator can raise that to 30 days at most.

30 days after a licence is removed

Exchange Online holds the mailbox for 30 days. Then it is deleted and no administrator or support ticket can bring it back.

Backup restores, it does not export

Microsoft's own backup service costs $0.15 per GB per month and restores mail into Microsoft 365. It does not produce a local file.

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.

Why Corbett

Why Choose Corbett Office 365 Backup Tool?

One licence

Covers Office 365 and 209+ other providers

No subscription

Lifetime price from $99

Read-only access

Nothing is deleted in Office 365

Direct connection

No Corbett server in between

Eight formats

Plus move to a new inbox

No size limit

Any mailbox size or message count

Free demo

10 emails saved per folder

30 day money back

Refund window on every licence

Before purchase

Outlook Export vs Office 365 Backup Tool

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

Task	Outlook export	Office 365 Backup Tool
Cost	Free with Outlook	$99 one time
One mailbox, once, to PST	Built for exactly that	Handles it too, plus the extra rows
Which Outlook	Classic Outlook. New Outlook exports mail only	Outlook not needed at all
Output format	PST only	PST, PDF, MBOX and five more
Date, sender or subject filter	Not in the export wizard	Applied before the backup
Several mailboxes	One account per export, one at a time	Queued together
Waiting on a sync first	The entire mailbox must download into Outlook	Pulls from the server directly
Headers and raw source	Not shown during export	Full preview before the backup

Rows tinted green are where Outlook wins.

One account, PST only and classic Outlook already installed: use Outlook and skip the purchase. Administrators who need many mailboxes without every 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 covered in Office 365 mailbox to PST. A finished PST converts to other formats with the email converter tool.

Global recognition

Office 365 Backup Tool Users Trust

Users rate Corbett backup software 4.6 out of 5 across 683 reviews, and software directories list it.

CNET
Download.io
UpdateStar
TopSoftware Advisor
SaaSHub
Uptodown

Specifications

Office 365 Backup Tool Specifications

Windows Versions Supported by Office 365 Backup Tool

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

Windows 11, 10, 8.1, 8 and 7, in 32 and 64 bit. Windows Server 2025 down to 2008. Outlook is not required.

No macOS or Linux build.

Corbett has built Windows email utilities since 2020. Support for Office 365 Backup Tool is handled by the team that wrote it.

Full specification

Office 365 Backup Sources and Output Formats

Complete source and output list for Corbett Office 365 Backup Tool.

Goes in

Microsoft 365 sources

Mail source: Microsoft 365 and Office 365 mailboxes on Exchange Online
Sign-in: Microsoft login window, Authenticator, SMS or security key
Server: Host and port detected automatically
Item types: Emails, attachments, inline images, contacts and calendar
Folders: All mail folders, Archive, Deleted Items, Junk and custom folders
Accounts per session: Several mailboxes, all with their own sign-in
Mailbox size limit: None, any mailbox size
Access mode: Read-only, nothing deleted in Microsoft 365
Filters: Dates, sender, recipient, subject, text, attachment, size
Local files opened: PST, OST, MBOX, EML, EMLX, MSG

Comes out

Backup destinations

Client formats: PST for Outlook, MBOX for Thunderbird and Apple Mail, EML, MSG
PST options: Unicode PST, split by size, merge mailboxes into one PST
Save locations: Folder, external drive, network share
Document formats: PDF, HTML, CSV, TXT
Contacts and calendar: vCard and ICS files next to the mail
Inbox destinations: Google Workspace, another Microsoft 365 account or any IMAP host
Separate extraction: Attachments, email addresses and phone numbers
If your line drops: A broken connection resumes
Reports: Live progress, log and CSV report
Restoring mail: Email Recovery Software

To convert saved files later, use email converter tool or PST File Converter Tool. To move a Microsoft 365 account to a new provider, use email migration tool. To open a saved file without exporting, use free email viewer software or Free PST Viewer Tool.

User testimonials

Office 365 Backup Tool Reviews From Users

Drawn from 683 reviews of the Corbett wizard behind Office 365 Backup Tool.

4.6 out of 5

Pulled from 683 reviews on rating sites and customer emails. Below are three, quoted exactly.

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

Best practice

How to Keep Your Office 365 Backup Safe

Saved mail is only useful if it opens later. These four habits protect your Microsoft 365 archive.

Back up before the licence goes

A removed licence deletes the mailbox 30 days later. Save the mail first.

Open a sample file

After saving, open a handful of messages. Confirm folders, attachments and dates came across.

Keep PST and PDF

Repeat the backup with a second format. PST for Outlook and PDF for a file that must open in ten years.

Store a copy off the account

Keep one copy on a disk that is not connected to the account, so ransomware or a bad sign-in cannot reach it.

Common questions

Office 365 Backup Tool Questions

Signing in, what is copied and where the 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?

Microsoft retired Basic Authentication for Exchange Online in October 2022, so typed passwords no longer reach a mailbox. The tool opens Microsoft's sign-in page, you authenticate there and Exchange Online returns an OAuth token. The program never sees your password.

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

Yes. Because sign-in happens on the Microsoft 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.

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

No. One mailbox is added per sign-in. Several can be queued and processed together, but every one needs its own sign-in. For the entire organization without every 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 like the main mailbox. 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?

Choose PST when the mail may go back into Outlook or another Microsoft 365 account later. Choose PDF when the copy is for someone without Outlook or for a legal or HR file that must open in ten years. Many people save both by repeating the backup.

Does the backup include Microsoft 365 contacts and calendar?

Yes, when the mailbox carries them. Contacts save 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. The backup is one way only, so the server copy stays 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 download speed, but nothing stops before the end. A dropped link resumes with the next unsaved item.

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 works on your PC and connects from there to Microsoft. The output lands on the disk or drive you select. Corbett stores nothing and relays nothing.

Does Office 365 Backup Tool work on Mac or Linux?

No. It needs Windows 7 or later, or Windows Server 2008 onward. Mac and Linux builds do not exist.

Can I trial the Office 365 tool for free?

Yes. The trial signs in to any Microsoft 365 tenant mailbox, loads all folders and unlocks preview and every filter. It saves the first 10 emails per folder, letting real tenant mail prove the output before purchase.

Can the Office 365 backup be scheduled?

No. Every backup is a full copy of the ticked folders. There is no scheduler, so a repeat backup starts by hand.

How much does Office 365 Backup Tool cost?

One payment of $99 buys a lifetime licence for up to 5 machines, with a 30 day refund window.

Does the tool delete mail from Microsoft 365?

No. It only reads the mailbox. Delete old folders yourself once the archive is checked.

Can I move Microsoft 365 mail to Google Workspace?

Yes. Use the email migration tool. See also Migrate email from Office 365 to Google Workspace.

How do I get Microsoft 365 mail into Outlook?

Save a PST. Steps are in Office 365 mailbox to PST, and a saved PST imports back into Microsoft 365.

Can I open a saved file without Outlook?

Yes. Open it read-only in the free email viewer software or the Free PST Viewer Tool.

Which Windows editions work?

Windows 11 through 7, in 32 or 64 bit, and Windows Server editions from 2008 through 2025.

Which folders are backed up?

Inbox, Sent Items, Drafts, the Archive folder, Deleted Items, Junk Email and custom folders, with subfolders kept in their original order.

Step by step

Office 365 Backup Guides for Common Tasks

Guides for jobs around an Office 365 backup.

Exporting Microsoft 365 mail

Switching tenants

Back Up Office 365 Mail Before the Licence Goes

Install the demo, sign in on Microsoft's page and save sample mail from every folder. A lifetime licence is one $99 payment with 30 days to ask for a refund.

Download free demo Purchase now

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