{"id":19457,"date":"2023-08-29T09:09:45","date_gmt":"2023-08-29T09:09:45","guid":{"rendered":"https:\/\/www.sandbox.backupassist.com\/blog\/?p=19457"},"modified":"2023-10-04T08:25:28","modified_gmt":"2023-10-04T08:25:28","slug":"mailbox-does-not-exist-errors-for-microsoft-365-mailbox-backups","status":"publish","type":"post","link":"https:\/\/www.sandbox.backupassist.com\/blog\/mailbox-does-not-exist-errors-for-microsoft-365-mailbox-backups","title":{"rendered":"\u201cMailbox does not exist\u201d errors for Microsoft 365 mailbox backups"},"content":{"rendered":"\t\t
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This blog article has been superseded by this article<\/a>.<\/strong><\/p><\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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<\/p>\n

In August 2023, Microsoft made unannounced changes to hosted Exchange Mailbox service in Microsoft 365 (formerly Office 365).<\/p>\n

<\/p>\n

<\/p>\n

These changes affect the \u201cContacts\u201d folder in everyone\u2019s mailboxes. It results in mailbox backups now aborting prematurely with the error, \u201cMailbox does not exist\u201d.<\/p>\n

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\"\"<\/figure>\n

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<\/p>\n

This misleading and factually incorrect error message comes directly from Microsoft, causing BackupAssist 365 to abort the current user mailbox and move to the next one.<\/p>\n

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<\/p>\n

We are aware of this situation, and are currently working around this problem.<\/strong><\/p>\n

<\/p>\n

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We wish to advise our users that:<\/p>\n

<\/p>\n

<\/p>\n

    \n
  1. We empathize with the frustration that this has caused.<\/li>\n
  2. This issue is caused by changes at Microsoft\u2019s end. It looks plainly like a bug, introduced and rolled out in August 2023.<\/li>\n
  3. We know this because BackupAssist 365 has been backing up Contacts for over 5 years, and that part of our code has not changed in that time. Yes, it\u2019s that stable.<\/li>\n
  4. We are now doing R&D into working around this Microsoft bugs.<\/li>\n<\/ol>\n

    <\/p>\n

    <\/p>\n

    Technical information about Microsoft\u2019s magical disappearing mailboxes<\/h2>\n

    <\/p>\n

    <\/p>\n

    BackupAssist\u2019s mailbox backup code is conceptually straightforward. When processing the Contact list, we:<\/p>\n

    <\/p>\n

    <\/p>\n

      \n
    1. Find a list of folders in a mailbox using the FindFolder request.<\/li>\n
    2. Get a list of items in each folder using the FindItem request.<\/li>\n<\/ol>\n

      <\/p>\n

      <\/p>\n

      This has worked for over 5 years against Microsoft\u2019s online Exchange offerings, and many more years against Exchange on-premise.<\/p>\n

      <\/p>\n

      <\/p>\n

      In August 2023, it stopped working. We investigated why, and found:<\/p>\n

      <\/p>\n

      <\/p>\n

        \n
      • FindFolder request (which also returns subfolders) is executed successfully.<\/li>\n
      • FindItem request for the same folder returns ErrorNonExistentMailbox.<\/li>\n<\/ul>\n

        <\/p>\n

        <\/p>\n

        In other words, we can see the folders in a user mailbox and we\u2019re told they exist\u2026 but when we try to look inside the folder, we\u2019re told that the entire Mailbox does not exist.<\/p>\n

        <\/p>\n

        <\/p>\n

        This is hard to believe, so here is the raw XML response for good measure:<\/p>\n

        <Trace Tag=\"EwsResponse\" Tid=\"4\" Time=\"2023-08-28 12:40:55Z\" Version=\"0.0.0.0\">
          <?xml version=\"1.0\" encoding=\"utf-8\"?>
          <s:Envelope xmlns:s=\"http:\/\/schemas.xmlsoap.org\/soap\/envelope\/\">
            <s:Header>
              <h:ServerVersionInfo MajorVersion=\"15\" MinorVersion=\"20\" MajorBuildNumber=\"6699\" MinorBuildNumber=\"34\" Version=\"V2018_01_08\" xmlns:h=\"http:\/\/schemas.microsoft.com\/exchange\/services\/2006\/types\" xmlns:xsd=\"http:\/\/www.w3.org\/2001\/XMLSchema\" xmlns:xsi=\"http:\/\/www.w3.org\/2001\/XMLSchema-instance\" \/>
            <\/s:Header>
            <s:Body>
              <m:FindItemResponse xmlns:m=\"http:\/\/schemas.microsoft.com\/exchange\/services\/2006\/messages\" xmlns:xsd=\"http:\/\/www.w3.org\/2001\/XMLSchema\" xmlns:xsi=\"http:\/\/www.w3.org\/2001\/XMLSchema-instance\" xmlns:t=\"http:\/\/schemas.microsoft.com\/exchange\/services\/2006\/types\">
                <m:ResponseMessages>
                  <m:FindItemResponseMessage ResponseClass=\"Error\">
                    <m:MessageText>Mailbox does not exist.<\/m:MessageText>
                    <m:ResponseCode>ErrorNonExistentMailbox<\/m:ResponseCode>
                    <m:DescriptiveLinkKey>0<\/m:DescriptiveLinkKey>
                  <\/m:FindItemResponseMessage>
                <\/m:ResponseMessages>
              <\/m:FindItemResponse>
            <\/s:Body>
          <\/s:Envelope>
        <\/Trace><\/pre>\n
        <\/p>\n
        <\/p>\n
        <\/p>\n
        <\/p>\n
        How is it possible that a mailbox suddenly does not exist, when only 1 API call prior, BackupAssist 365 was happily talking to and querying that mailbox?<\/p>\n
        <\/p>\n
        <\/p>\n
        The answer can only be Microsoft magic.<\/p>\n
        <\/p>\n
        <\/p>\n
        Why the mailbox backup gets aborted<\/h2>\n
        <\/p>\n
        <\/p>\n
        Unfortunately, this error message also causes BackupAssist 365 to abort the mailbox. \u201cMailbox does not exist\u201d is classed as a terminal error. So there\u2019s no point in trying to back up a mailbox that does not exist \u2013 is there?<\/p>\n
        <\/p>\n
        <\/p>\n
        But sadly, there are times where common sense and logic don\u2019t work \u2013 and this appears to be one of them.<\/p>\n
        <\/p>\n
        <\/p>\n
        What does our hotfix do?<\/h2>\n
        <\/p>\n
        <\/p>\n
        It seems clear that we cannot trust the error messages that get returned in this case.<\/p>\n
        <\/p>\n
        <\/p>\n
        Our hotfix skips over folders that show this error, and proceed with the next folder anyway.<\/p>\n
        <\/p>\n
        <\/p>\n
        This will at least allow the backups to continue, until Microsoft fix the actual problem. Your backup reports will now show an informational message, reporting which Contacts folders could not be backed up.<\/b>\u00a0This message will simply go away when Microsoft fixes the problem.<\/p>\n
        <\/p>\n
        <\/p>\n
        This hotfix was first made available on 30 August 2023. If we receive positive user feedback, we will roll this into the mainstream release within 2-3 days.<\/b><\/p>\n
        <\/p>\n
        <\/p>\n
        To all our users of BackupAssist 365 who rely on our software for backing up Microsoft 365: thank all our users for their patience and understanding\u2026 <\/strong>we at BackupAssist are trying to make the best of a thoroughly unsatisfactory situation.<\/p>\n
        <\/p><\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t\t\t<\/div>\n\t\t\t<\/div>\n\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"
        Microsoft recently made changes to the Contacts folders in user mailboxes, which has broken their own API and caused BackupAssist 365 backups to stop. We have just produced an emergency workaround – please read on for the details.<\/p>\n","protected":false},"author":2,"featured_media":19469,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[763],"tags":[],"class_list":["post-19457","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-backupassist-365"],"yoast_head":"\n\u201cMailbox does not exist\u201d errors for Microsoft 365 mailbox backups - Cyber Resilience Blog<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.sandbox.backupassist.com\/blog\/mailbox-does-not-exist-errors-for-microsoft-365-mailbox-backups\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"\u201cMailbox does not exist\u201d errors for Microsoft 365 mailbox backups - Cyber Resilience Blog\" \/>\n<meta property=\"og:description\" content=\"Microsoft recently made changes to the Contacts folders in user mailboxes, which has broken their own API and caused BackupAssist 365 backups to stop. 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He founded BackupAssist in 2002 \u2014 making him one of the longest-standing voices in Windows backup and data protection \u2014 and has spent the decades since talking to IT administrators around the world about what actually goes wrong, and why. His interest in data loss isn't abstract. Early in his career, he was working at the Monash University help desk when a student came in with a floppy disk that wouldn't read. They tried everything. None of their drives could read it either. The disk held her entire PhD dissertation \u2014 years of work \u2014 and it was the only copy. She broke down in tears. There was nothing he could do. Five years later, he wrote the first version of BackupAssist. Linus holds a Bachelor of Science in Computer Science and has held Microsoft Certified Solution Developer and Sun Certified Java Programmer credentials. More recently, he has completed digital forensics and cyber-security courses through the Black Hat Conference. He has spoken on information security and cryptography at Infosecurity Europe, addressed politicians and policymakers at Australian Parliament House, presented to SMB IT administrators at the IT Pro Experts Conference, and served as a guest lecturer to Cyber Security master's students at the University of Melbourne. On this blog, Linus writes about backup strategy and the technical side of cyber-resilience \u2014 drawing on 24 years of product development and direct conversation with the IT professionals BackupAssist is built for. 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He founded BackupAssist in 2002 \u2014 making him one of the longest-standing voices in Windows backup and data protection \u2014 and has spent the decades since talking to IT administrators around the world about what actually goes wrong, and why. His interest in data loss isn't abstract. Early in his career, he was working at the Monash University help desk when a student came in with a floppy disk that wouldn't read. They tried everything. None of their drives could read it either. The disk held her entire PhD dissertation \u2014 years of work \u2014 and it was the only copy. She broke down in tears. There was nothing he could do. Five years later, he wrote the first version of BackupAssist. Linus holds a Bachelor of Science in Computer Science and has held Microsoft Certified Solution Developer and Sun Certified Java Programmer credentials. More recently, he has completed digital forensics and cyber-security courses through the Black Hat Conference. He has spoken on information security and cryptography at Infosecurity Europe, addressed politicians and policymakers at Australian Parliament House, presented to SMB IT administrators at the IT Pro Experts Conference, and served as a guest lecturer to Cyber Security master's students at the University of Melbourne. On this blog, Linus writes about backup strategy and the technical side of cyber-resilience \u2014 drawing on 24 years of product development and direct conversation with the IT professionals BackupAssist is built for. 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