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BackupAssist365 v1.22.1 (120 MB)

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Best practice guides

BackupAssist 365

Cheat Sheet for Microsoft 365 (Office 365) backups

  • Getting started and installation
  • Setting up your backup jobs
  • Scheduling, backup windows and your first full backup
  • Backup History, Deleted Items, Old Versions, and Restore
  • Managing your backup destination
  • Data security

Release notes

BackupAssist 365 v1.22.1

Release notes (14 Mar 2024)


  • Mailbox restore bug: fix for restoring the “Recoverable Items” folder when moved to “Historical Items”. This means that items that have been purged from Recoverable Items are now restored correctly.
  • Clearer display of MBC licensing interactions, when temporary internet downtime results in unsuccessful license refreshing.
  • Mailbox backup resilience: when ErrorTooManyObjectsOpened errors are returned from Exchange, handle this by reducing the number of items requested and retrying. Previously, this case triggered a bug where the same items would be retried endlessly and the PST file would grow.
  • Mailbox backup resilience to Exchange outages: better handling when Exchange Online returns a 503 server unavailable error. Previously an error message “The given key was not present in the dictionary.” would appear. Now the 503 error is treated as a “server busy” exception, and the operation will be retried automatically.
  • Workaround for downloading files that have modification date of 1/1/1970 or earlier. Prior to the workaround, a “OSError [Errorno 22]” would appear in the backup report.
  • GUI fix: make full error message visible when user enters an invalid license key.
  • German build: the help link that appears in the backup report when there are warnings or errors now directs to the German version of the knowledge base.

BackupAssist 365 v1.21.0

Release notes (23 Jan 2024)


  • Speed enhancements – listing mailbox folders is now 3 to 5 times faster, resulting in overall improvements in backup time between 10% to 40%, depending on the data.
  • Fix where editing a job and closing the GUI will cause BA365 to still think the job is being edited and prevent the backup job from running until it is edited again.
  • Improved error message where there is a misconfiguration with the backup user.
  • Remove basic authentication as an option (no longer supported by Exchange).

BackupAssist 365 v1.20.2

Release notes (14 Dec 2023)


  • Clean up temporary files left behind by Microsoft’s buggy Exchange Online PowerShell library.
  • Restore for SharePoint, OneDrive – sort user and group and site selection windows alphabetically.
  • File Restore: detect when versioning has been used, even if the backup metadata file has been damaged or deleted.
  • Mailbox backup: performance improvement by removing duplicate read operations.

BackupAssist 365 v1.19.1

Release notes (5 Oct 2023)

This release includes a full fix for the “Mailbox does not exists” error for Microsoft 365 mailbox backups. It is a follow up release to the initial fix provided in v1.18.1.

IMPORTANT – This release requires granting impersonation rights to the backup user.

This release provides a future proof solution, but also requires a change in the Backup User configuration.

For further details, please read the following blog article.

BackupAssist 365 v1.18.1

Release notes (30 Aug 2023)

Recently, Microsoft introduced a critical issue in their hosted mailbox service in Microsoft 365 (Office 365).

This causes backup failures and we believe it will affect all our users.

An explanation of how Microsoft caused these problems is provided in our blog article on this subject.
Use the links above to download a workaround for this problem.

For the time being, it seems that Contacts cannot be accessed anymore. You will see informational messages in the backup reports noting the issues. However, the important thing is that your mailbox backups will continue and all the other contents of your mailboxes will be backed up.

We will keep researching this issue and post updates accordingly.

BackupAssist 365 v1.17.2


  • Improved detection of missing prerequisite software – such as PowerShell version, .NET framework, and so on.

BackupAssist 365 v1.17.1


  • Bug fix for refreshing tokens, using new Exchange Online API.

BackupAssist 365 v1.17.0


  • Changed over to new Exchange Online API (EXO v3), replacing the previous Remote PowerShell API, which has been discontinued by Microsoft.

BackupAssist 365 v1.16.0

Bug fix:

  • Back up mailboxes and ODB by group – handle cases where a group contains non-users.

GUI helpfulness:

  • Detect when remote PowerShell is disabled for a user, and display a helpful message.
  • Sort the list of files, folders and Document Libraries alphabetically, ignoring case.
  • Better tool tips for setting inclusions and exclusions for multi-site SharePoint backups.

Error handling:

  • SharePoint backup setup – handle throttling when getting list of sites on European tenants where M365 is buggy and returns incorrectly formatted integers.

BackupAssist 365 v1.15.1


  • Fixed a bug that was in v1.15.0

BackupAssist 365 v1.15.0


  • Mailbox backups: Show duration for each mailbox in the email summary.
  • Mailbox backups: Allow CSV file upload for on-premise Exchange mailbox backups.
  • Mailbox backups: Fixed edge-case bug in PST rebuild where the rebuild happens repeatedly.
  • Sort user and group selections alphabetically in the GUI.

BackupAssist 365 v1.14.0


  • Duration for each individual mailbox is shown in the backup report.
  • Fixed a hanging problem with certain date filters.
  • Deals with new cases where email attachments cannot be downloaded due to failures within Exchange Online (Microsoft’s bugs).
  • Dropbox backups now work with updated security policies (previously the backup would stop after 4 hours).
  • Improved logging for mailbox backups to aid our technical support.
  • Improved handling of SEH Exception to add resilience to hardware faults and I/O errors.

BackupAssist 365 v1.13.1


  • Pre-populate network credentials when setting up backups or restores to a network share.
  • Fix a bug in v1.12 where mailbox backups to a network share did not work
  • Update the Dropbox interface to work with latest changes.
  • Remove OneDrive consumer version as a supported source of data.

BackupAssist 365 v1.12.0


  • Allow restore from network share.
  • Automatically populate network share credentials based on existing backup tasks using the same file server.
  • Start the service faster.

BackupAssist 365 v1.11.3


  • Upgraded to 64-bit application.
  • Now works with Office 365 tenants with non “.com” domain names – such as
  • Fixed bug where SharePoint sites were sometimes included in the user license count.

BackupAssist 365 v1.10.1


  • Speed improvements with file downloads.
  • Changed expired license grace period to 14 days.
  • Miscellaneous stability enhancements

BackupAssist 365 v1.9.13

Bug fixes:

  • Fixed a bug preventing the setup of new backup tasks for OneDrive For Business – Multi User, and SharePoint.

BackupAssist 365 v1.9.12

Bug fixes:

  • Fixed an error preventing connections to Dropbox.
  • Improved log file rotation.


  • Password protection for the GUI Console.

BackupAssist 365 v1.9.11

Bug fixes:

  • Clearer logging messages if a backup failure occurs.


  • O365 Mailbox & OneDrive for Business – allow user selection by group.
  • Performance improvements when backing up files.
  • If a corruption is detected in a PST file, automatically rebuild the corrupted file.

BackupAssist 365 v1.9.10.1

Bug fixes:

  • Fix for multiple BA365 license usage where one O365 user id is associated with two or more O365 usernames.
  • Fix for incorrect email reporting (due to SQL database error).

BackupAssist 365 v1.9.10


  • PST Rebuild tool.
  • Automatic permissions settings for Exchange 2016/2019 on-premise.
  • Show restore options for beta sources (Dropbox, Box, SFTP).
  • Include licensing info in diagnostics.

BackupAssist 365 v1.9.9

Mailbox restore enhancements: 

  • Fixed issue where Office 365 starts throttling when there are large emails / attachments.

File restore enhancements:

  • Provide the option to use an existing backup login instead of always requiring the user to authenticate again.
  • Prevent the user from incorrectly restoring ciphertext versions of encrypted files by navigating directly into the backup directory.

SharePoint backup enhancements:

  • Work-around problems where SharePoint Online incorrectly reports a 0 file length for particular files

BackupAssist 365 v1.9.8


  • SharePoint:
    • Improved guidance when working with a new backup user.

Bug fixes:

  • Improved memory usage for mailbox backups, avoiding out of memory errors.

BackupAssist 365 v1.9.7


  • Mailbox restore enhancements:
    • selectively restore Historical Items, Recoverable Items, In-Place Archives.

  • On-Premise Exchange:
    • allow backup of public folders via multi-user backup jobs.

  • SharePoint / OneDrive:
    • retry files when O365 incorrectly reports file lengths.

Bug fixes:

  • excessive memory usage when file copy errors occur.
  • errors now appear in the restore report.

BackupAssist 365 v1.9.6


  • Better guidance to user when setting up multiple backups, to avoid having to log in multiple times
  • Improved handling on slow virtualised systems where the OS fails to start the BA365 service automatically. (SCM retries and service checking within the GUI)
  • Packaged the PSTRebuild tool via command line interface, which helps with corrupted PST files.

Bug fixes:

  • Fixed restoring to OneDrive for Business in multi-user and single-user scenarios (occasional permissions issues)
  • Fixes when handling network outages:
    • Improved retries for token refresh operations
    • GUI handling when setting up SharePoint backups

BackupAssist 365 v1.9.5

Back up multiple SharePoint sites from within a single backup job, including subsites

Improved handling for IMAP servers that do not support NOOP command.

BackupAssist 365 v1.9.4

OneDrive for Business restore to original location

Mailbox backups – include permanently deleted items from the Recoverable Items folder

Mailbox backups – include the In-place Archives folder in the PST backup

BackupAssist 365 v1.9.3

Mailbox restore from PST to live mailbox in Office 365

BackupAssist 365 v1.9.2

Validation of backup user permissions

German builds with handling for CP853 code page Operating Systems

BackupAssist 365 v1.9.1.1

Best practice tips built into the software helps users set up the configuration correctly

Ability to back up SharePoint subsites

Improved resilience to network outages for file backups, with automatic retries on listing OneDrive users, listing directories, etc.

Restoring from NAS – detailed error message if user connects with multiple sets of different credentials.

Bug fix: service won’t stop properly if a user has attempted a restore.

BackupAssist 365 v1.9.1

New, friendlier Graphical User Interface (GUI)

BackupAssist 365 v1.9.0.5

Provides command line interface for batch mailbox restore.

Display license status in the backup report.

Ignore the “Internal Server Error” in Exchange Server that is caused when trying to back up appointments created by Microsoft Teams when one of the recipients has a bad email address, triggering an “Undeliverable” message.

Fix some HTML scrolling issues at the top of email reports, to make them read better on mobile devices.

BackupAssist 365 v1.9.0.4

Limit the length of the PST password in the GUI.

Fetch all users for OneDrive for Business, not just the first 100.

More resilient parsing of multi-mailbox usernames/passwords when supplied via CSV file or clipboard.

Fixed rare cases where system problems can stop Mailbox backups from running, causing them to hang at “Connecting…”. Instead, BackupAssist 365 will gracefully handle this and attempt the backup at the next scheduled time.

BackupAssist 365 v1.9.0.3

Mailboxes: fixed “Error 1168” if two duplicated items in a folder are moved where one item is deleted and another is moved to a different folder.

SharePoint: fixed crash when listing SharePoint sites if one site contains Extended ASCII characters but not unicode characters in its name.

SharePoint & OneDrive for Business: handle out of disk space and stop the backup preemptively to avoid system problems

Fix problem where email reports were not sent if using ASCII reports via the BackupAssist cloud service.

Fixed GUI crash when viewing skipped items for a deleted backup task.

BackupAssist 365 v1.9.0.2

Mailbox backups: handle situations where there’s throttling or internal Office 365 failures. These used to result in backup failures. Now instead, automatic retries are attempted.

OneDrive for Business: fix false positive warnings that a user’s private files cannot be backed up.

Handle file backups where the file was updated during the backup run.

BackupAssist 365 v1.9.0.1

Fix token expiry problem where some tasks stop running after 90 days.

Fix bug where a Mailbox backup hangs if the entire mailbox is throttled when connecting.

BackupAssist 365 v1.9.0.0

SharePoint backups now free; implemented license usage reports.

Stability enhancements for file downloads.


BackupAssist 365 v1.8.2


Backup Windows: implement a maximum run time to stop a backup if it runs too long.

File downloads: temp files are now used when downloading files to eliminate possibility of corruption in the event of hardware failure or power outage.

File downloads: deal with temporary cloud outages with automatic retries

SharePoint: Automatic permissions granting on demand so you can backup sites that you don’t have permissions to yet.

Mailbox downloads: preserve folder path when moving deleted items to Historical Items

BackupAssist 365 v1.8.1


OneDrive for Business enhancements:

  • Automatic permissions granting to the backup user – all you need is a backup user with SharePoint Admin and Application Admin roles, and OneDrive for Business backups will work seamlessly
  • Better handling of edge cases like network timeouts, intermittent O365 outages and throttling
  • Validation to catch invalid file selections

Diagnostics enhancements:

  • When you submit diagnostics to us, a summary of the backup configuration is now generated to make debugging easier.

Bug fixes:

  • Fixed bug where undo delete worked but the GUI was not updated
  • Fixed bug where multi-user O365 / Exchange backup tasks were detected as single-user tasks in the Edit Task GUI.

BackupAssist 365 v1.8.0


Numerous enhancements in the Progress & Log user interface:

  • Filter the view of active backups by backup task and date
  • View past backup reports
  • See which items are skipped during a backup – such as emails with attachments that failed a virus scan

Reporting enhancements:

  • Only include warnings and errors in the top section of backup reports.

Mailbox backup enhancements:

  • Fast reconnections after network problems
  • Write protect PST files, and include a readme.txt to discourage users from opening the backup files directly.

Bug fixes:

  • Fixed bug where Public Folder backup was not working.
  • Fixed bug where multi-user IMAP backup tasks were detected as single-user tasks in the Edit Task GUI.


BackupAssist 365 v1.7.1


User experience enhancements:

  • Always use private browsing mode by default when logging in to Office 365
  • Expanded list of supported browsers for authenticating – IE, Edge, Firefox, Opera, Chrome, AVG, Brave
  • Improved calendar control allows faster input of months and years

Network Share support as a destination

Mailbox backup enhancements:

  • Support for TLS 1.2 connections – required when TLS 1.0 and 1.1 are disabled on an Exchange Server
  • Compatibility with Exchange Server 2019

BackupAssist 365 v1.7.0

Support modern authentication for Mailbox downloads:

  • Allow user to log in via web browser.
  • Allow user to connect when MFA is turned on.

SharePoint enhancements:

  • Support backing up multiple Document Libraries per SharePoint Site, from a single backup task and login

Store application save data to the ProgramData directory instead of the system user profile directory.

Bug fixes:

  • Fixed bug where occasionally, active backup logs would disappear if the GUI is running for over 7 days.

BackupAssist 365 v1.6.2

Mailbox backup enhancements:

  • Handle throttling situations with users who have thousands of Calendar items. Around 500-1000 calendar items can be downloaded per day, before O365 starts to throttle. Upon throttling, BA365 will skip the folder and continue with the remainder of the mailbox. In practice, this means the calendar will now be downloaded over several days, while remaining data is backed up correctly.

Support for community builds:

  • The same licence key will now work with community builds and official release builds.

Bug fixes:

  • Fixed bug where “Suggested Contacts” folder on German systems with data from Outlook 2010 was crashing the backup.
  • Fixed bug where SharePoint and OneDrive for Business backups will correctly terminate if the network connection has been down for over 10 minutes, and all attempts to reconnect have failed.

BackupAssist 365 v1.6.1

Mailbox backup enhancements:

  • Connect to Office 365 using the Exchange 2016 interface, instead of Exchange 2013. This solves issues where error messages from Office 365 like “The property Hashtags is valid only for Exchange Exchange2015 or later versions.” are shown.

Improved reporting:

  • Introduced a new Info level for report messages, so small issues can be logged without generating warnings or errors. This is mainly to deal with edge cases that are inconsequential, and should not demand attention from the administrator, because they make no tangible difference to the integrity of the backups. Examples of this are:
    1. An email attachment contains a virus, so the email is skipped over in the backup.
    2. There was a transient error in Office 365 (service temporarily unavailable) so a folder or file was skipped, but it will be backed up next time the backup runs. This handles error messages such as “Specified object not found in store”.
    3. Office 365 is internally moving data around in its datacenters, resulting in messages such as “Exchange Web Services are not currently avaialble for this request because none of the Client Access Servers in the destination site could process the request” or “Mailbox move in progress”

Allow the Service to run as different user identity without losing configuration settings:

  • The configuration encryption key is now derived from the system identity, not the user identity.

Bug fixes:

  • Fixed bug in Mailbox backups where reserved characters such as “, <, >, in a folder name will cause a backup failure.

BackupAssist 365 v1.6.0

Mailbox backup enhancements:

  • PST files are now extremely compact, with upwards of 99% space utilisation.
  • Handle throttling better: if one mailbox is throttled, BA365 will detect this and skip over to the next mailbox, so that one throttled mailbox will not halt the entire backup.
  • Implemented a maximum number of retries per throttled mailbox.

OneDrive for Business enhancements:

  • Support for backing up multiple user accounts from a single backup task and login.

Improved reporting:

  • Skipped item messages are now logged against the mailbox or user storage account, instead of globally.
  • Handle Office 365 transient errors better: “Mailbox Move in Progress”, “The specified object not found in store” now only generates a warning, not a failure.

Bug fixes:

  • Fixed bug for SharePoint and OneDrive for Business backups where files that contain a ‘#’ character would be skipped and raise an error.