{"id":16924,"date":"2026-06-17T13:01:55","date_gmt":"2026-06-17T04:01:55","guid":{"rendered":"https:\/\/m365jp.net\/?p=16924"},"modified":"2026-06-17T13:06:30","modified_gmt":"2026-06-17T04:06:30","slug":"servicedegradation-ex1386636-exchange-online-users-may-be-unable-to-see-the-free-busy-status-of-multiple-cross-tenant-mailboxes-in-exchange-online","status":"publish","type":"post","link":"https:\/\/m365jp.net\/index.php\/2026-06-17-servicedegradation-ex1386636-exchange-online-users-may-be-unable-to-see-the-free-busy-status-of-multiple-cross-tenant-mailboxes-in-exchange-online","title":{"rendered":"[serviceDegradation] EX1386636 | Exchange Online | Users may be unable to see the free\/busy status of multiple cross-tenant mailboxes in Exchange Online"},"content":{"rendered":"
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EX1386636 | Exchange Online | Users may be unable to see the free\/busy status of multiple cross-tenant mailboxes in Exchange Online<\/th>\n<\/tr>\n<\/tbody>\n<\/table>\n
\n\n\n\n\n\n\n\n\n\n\n
Status<\/th>\nserviceDegradation<\/td>\n<\/tr>\n
Classification<\/th>\nadvisory<\/td>\n<\/tr>\n
User Impact<\/th>\nUsers may be unable to see the free\/busy status of multiple cross-tenant mailboxes in Exchange Online.<\/td>\n<\/tr>\n
Last Updated<\/th>\n06\/17\/2026 03:05:13<\/td>\n<\/tr>\n
Start Time<\/th>\n05\/14\/2026 00:00:00<\/td>\n<\/tr>\n
End Time<\/th>\n<\/td>\n<\/tr>\n
Latest Message<\/th>\nTitle: Users may be unable to see the free\/busy status of multiple cross-tenant mailboxes in Exchange Online<\/p>\n

User impact: Users may be unable to see the free\/busy status of multiple cross-tenant mailboxes in Exchange Online.<\/p>\n

More info: This impact occurs only when two or more mailbox statuses are requested.<\/p>\n

Current status: We’ve validated that the source of impact was a NetCore deployment, which introduced a regression where headers were being dropped during free\/busy status requests for cross-tenant scenarios, resulting in back-end authentication requests failing. Our fix to address the regression is currently at 90 percent saturation in the affected environment, and we’ve reached out to affected users to begin testing for remediation.<\/p>\n

Scope of impact: Users attempting to access the free\/busy status of multiple mailboxes at once may be impacted.<\/p>\n

Start time: Thursday, May 14, 2026, at 12:00 AM UTC<\/p>\n

Root cause: A NetCore deployment introduced a regression where headers were being dropped during free\/busy status requests for cross-tenant scenarios, resulting in back-end authentication requests failing.<\/p>\n

Next update by: Wednesday, June 17, 2026, at 8:30 PM UTC<\/td>\n<\/tr>\n

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\u958b\u59cb\u6642\u9593:2026\u5e745\u670814\u65e5\u6728\u66dc\u65e5 0:00 UTC<\/p>\n

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EX1386636 | Exchange Online | Users may be unable to see the free\/busy status of multiple cross-tenant mailbox […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-16924","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/m365jp.net\/index.php\/wp-json\/wp\/v2\/posts\/16924","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/m365jp.net\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/m365jp.net\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/m365jp.net\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/m365jp.net\/index.php\/wp-json\/wp\/v2\/comments?post=16924"}],"version-history":[{"count":0,"href":"https:\/\/m365jp.net\/index.php\/wp-json\/wp\/v2\/posts\/16924\/revisions"}],"wp:attachment":[{"href":"https:\/\/m365jp.net\/index.php\/wp-json\/wp\/v2\/media?parent=16924"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/m365jp.net\/index.php\/wp-json\/wp\/v2\/categories?post=16924"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/m365jp.net\/index.php\/wp-json\/wp\/v2\/tags?post=16924"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}