{"id":17211,"date":"2026-07-09T09:01:41","date_gmt":"2026-07-09T00:01:41","guid":{"rendered":"https:\/\/m365jp.net\/?p=17211"},"modified":"2026-07-09T09:06:27","modified_gmt":"2026-07-09T00:06:27","slug":"mc1420903-exchange-online-will-prevent-creation-of-duplicate-dynamic-distribution-groups","status":"publish","type":"post","link":"https:\/\/m365jp.net\/index.php\/2026-07-09-mc1420903-exchange-online-will-prevent-creation-of-duplicate-dynamic-distribution-groups","title":{"rendered":"MC1420903 | Exchange Online will prevent creation of duplicate Dynamic Distribution Groups"},"content":{"rendered":"
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MC1420903 | Exchange Online will prevent creation of duplicate Dynamic Distribution Groups<\/th>\n<\/tr>\n<\/tbody>\n<\/table>\n
\n\n\n\n\n\n\n\n\n
Classification<\/th>\nstayInformed<\/td>\n<\/tr>\n
Last Updated<\/th>\n07\/08\/2026 23:16:14<\/td>\n<\/tr>\n
Start Time<\/th>\n07\/08\/2026 23:15:59<\/td>\n<\/tr>\n
End Time<\/th>\n09\/07\/2026 07:00:00<\/td>\n<\/tr>\n
Message Content<\/th>\n\n

[What and Why:]<\/b><\/p>\n

We are introducing a reliability improvement to Dynamic Distribution Groups (DDGs)<\/b> in Exchange Online. To prevent unnecessary duplication and reduce administrative overhead, Exchange Online will block the creation of new DDGs that are exact <\/b>duplicates of existing ones. This prevents redundant groups from quietly accumulating and counting toward your organization’s DDG limit without adding any capability. <\/p>\n

[Rollout Schedule:]<\/b><\/p>\n

<\/p>\n

    <\/p>\n
  • General Availability (Worldwide): Beginning late July 2026<\/b> and expected to complete by early August 2026<\/b><\/li>\n

    <\/p>\n

  • General Availability (GCC): Beginning early August 2026<\/b> and expected to complete by early August 2026<\/b><\/li>\n
  • General Availability (GCC High): Beginning early August 2026<\/b> and expected to complete by mid-August<\/b> 2026<\/b><\/li>\n
  • General Availability (DoD): Beginning mid-August 2026<\/b> and expected to complete by late August 2026<\/b><\/li>\n

    <\/ul>\n

    [Impact on Your Organization:]<\/b><\/p>\n

    <\/p>\n

    Who is affected:<\/b><\/p>\n

    <\/p>\n

      <\/p>\n
    • Exchange administrators managing Dynamic Distribution Groups<\/li>\n

      <\/p>\n

    • Organizations using automation or scripts to create DDGs<\/li>\n

      <\/ul>\n

      Platforms\/Services:<\/b><\/p>\n

      <\/p>\n

        <\/p>\n
      • Exchange Online<\/li>\n

        <\/p>\n

      • Exchange Admin Center (EAC)<\/li>\n

        <\/p>\n

      • Exchange Online PowerShell (New-DynamicDistributionGroup)<\/li>\n

        <\/ul>\n

        What will happen:<\/b><\/p>\n

        <\/p>\n

          <\/p>\n
        • Creation of a new DDG will be blocked<\/b> when all of the following are identical<\/b> to an existing DDG:\n
            <\/p>\n
          • Recipient filter<\/li>\n
          • Delivery management settings<\/li>\n
          • Message approval (moderation) settings<\/li>\n
          • Delegation settings<\/li>\n
          • Message visibility settings<\/li>\n<\/ul>\n<\/li>\n
          • When this occurs, the system will return an error indicating that a matching Dynamic Distribution Group already exists.<\/li>\n
          • If any one of these settings differs, the new DDG is not a duplicate and can be created normally.<\/li>\n
          • In most cases, you can use the existing DDG instead of creating a new one.<\/li>\n
          • Existing DDGs are not affected and will continue to function normally.<\/li>\n
          • This change is enforced at creation time only (no retroactive changes).<\/li>\n<\/ul>\n

            [Action Required \/ Recommendations:]<\/b><\/p>\n

            <\/p>\n

Machine Translation<\/th>\n\n

[\u4f55\u3068\u306a\u305c:]<\/b><\/p>\n

Exchange Online\u306e \u52d5\u7684\u914d\u5e03\u30b0\u30eb\u30fc\u30d7(DDG)<\/b> \u306b\u4fe1\u983c\u6027\u5411\u4e0a\u3092\u5c0e\u5165\u3057\u307e\u3059\u3002\u4e0d\u8981\u306a\u91cd\u8907\u3092\u9632\u304e\u3001\u7ba1\u7406\u4e0a\u306e\u8ca0\u62c5\u3092\u6e1b\u3089\u3059\u305f\u3081\u306b\u3001Exchange Online\u306f\u65e2\u5b58\u306eDDG\u3068 \u307e\u3063\u305f\u304f\u540c\u3058 <\/b>\u3082\u306e\u3068\u306a\u308b\u65b0\u898fDDG\u306e\u4f5c\u6210\u3092\u30d6\u30ed\u30c3\u30af\u3057\u307e\u3059\u3002\u3053\u308c\u306b\u3088\u308a\u3001\u5197\u9577\u306a\u30b0\u30eb\u30fc\u30d7\u304c\u9759\u304b\u306b\u84c4\u7a4d\u3055\u308c\u3066\u7d44\u7e54\u306eDDG\u5236\u9650\u306b\u30ab\u30a6\u30f3\u30c8\u3055\u308c\u308b\u306e\u3092\u9632\u304e\u3001\u6a5f\u80fd\u3092\u8ffd\u52a0\u305b\u305a\u306b\u6e08\u3080\u3002 <\/p>\n

[\u5c55\u958b\u30b9\u30b1\u30b8\u30e5\u30fc\u30eb:]<\/b><\/p>\n

<\/p>\n