{"id":14928,"date":"2026-02-12T05:01:14","date_gmt":"2026-02-11T20:01:14","guid":{"rendered":"https:\/\/m365jp.net\/?p=14928"},"modified":"2026-02-12T05:01:27","modified_gmt":"2026-02-11T20:01:27","slug":"servicedegradation-ex1228240-exchange-online-users-mailtips-may-not-reflect-free-busy-correctly-in-outlook-desktop-and-crashes-may-occur-when-adding-mailboxes-2","status":"publish","type":"post","link":"https:\/\/m365jp.net\/index.php\/2026-02-12-servicedegradation-ex1228240-exchange-online-users-mailtips-may-not-reflect-free-busy-correctly-in-outlook-desktop-and-crashes-may-occur-when-adding-mailboxes-2","title":{"rendered":"[serviceDegradation] EX1228240 | Exchange Online | Users&#8217; MailTips may not reflect free\/busy correctly in Outlook desktop and crashes may occur when adding mailboxes"},"content":{"rendered":"<div class=\"postie-post\">\n<div>\n<hr>\n<table id=\"section\">\n<tbody>\n<tr>\n<th width=\"95%\">EX1228240 | Exchange Online | Users&#8217; MailTips may not reflect free\/busy correctly in Outlook desktop and crashes may occur when adding mailboxes<\/th>\n<\/tr>\n<\/tbody>\n<\/table>\n<hr>\n<table id=\"data\">\n<tbody>\n<tr>\n<th>Status<\/th>\n<td class=\"bad\">serviceDegradation<\/td>\n<\/tr>\n<tr>\n<th>Classification<\/th>\n<td>advisory<\/td>\n<\/tr>\n<tr>\n<th>User Impact<\/th>\n<td>Users&#8217; MailTips may not reflect free\/busy correctly in Outlook desktop and crashes may occur when adding mailboxes.<\/td>\n<\/tr>\n<tr>\n<th>Last Updated<\/th>\n<td>02\/11\/2026 19:42:34<\/td>\n<\/tr>\n<tr>\n<th>Start Time<\/th>\n<td>02\/06\/2026 18:45:07<\/td>\n<\/tr>\n<tr>\n<th>End Time<\/th>\n<td><\/td>\n<\/tr>\n<tr>\n<th>Latest Message<\/th>\n<td>Title: Users&#8217; MailTips may not reflect free\/busy correctly in Outlook desktop and crashes may occur when adding mailboxes<\/p>\n<p>  User impact: Users&#8217; MailTips may not reflect free\/busy correctly in Outlook desktop and crashes may occur when adding mailboxes.<\/p>\n<p>  More info: This issue is specific to the Outlook desktop client in organizations with a hybrid environment using Exchange Web Services (EWS) for MailTips. Users may notice that the MailTips free\/busy feature isn\u2019t operating as expected and may see an error   stating \u201cwe can\u2019t show MailTips right now.\u201d<\/p>\n<p>  The Outlook desktop crashes occur when attempting to add a new on-premises mailbox.<\/p>\n<p>  Admins may be unable to create new on-premises mailboxes, and their cross-tenant AutoDiscover requests general may fail from hybrid environments.<br \/>  While we work on deploying the fix, admins may be able to mitigate the impact by restarting the Autodiscover app pool.<\/p>\n<p>  Current status: Our monitoring of the deployment of the fix to prevent the header duplication issue indicates that the majority of admins should be experiencing remediation, and we&#8217;re beginning to validate impact resolution with a subset of affected admins   as the saturation of the fix fully completes.<\/p>\n<p>  Scope of impact: Any admins\u2019 cross-tenant AutoDiscover requests may fail from hybrid environments, causing MailTips free\/busy not to show and crashing for users\u2019 Outlook desktop clients when adding additional on-premises mailboxes. This information may be updated   as our investigation continues.<\/p>\n<p>  Start time: Tuesday, January 27, 2026, at 12:30 AM UTC<\/p>\n<p>  Root cause: A routing change for Autodiscover requests introduced a header duplication issue causing a backlog of requests that ultimately fail or timeout, resulting in the impact.<\/p>\n<p>  Next update by: Wednesday, February 18, 2026, at 2:00 AM UTC<\/td>\n<\/tr>\n<\/tbody>\n<\/table><\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>EX1228240 | Exchange Online | Users&#8217; MailTips may not reflect free\/busy correctly in Outlook desktop and [&hellip;]<\/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-14928","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/m365jp.net\/index.php\/wp-json\/wp\/v2\/posts\/14928","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=14928"}],"version-history":[{"count":0,"href":"https:\/\/m365jp.net\/index.php\/wp-json\/wp\/v2\/posts\/14928\/revisions"}],"wp:attachment":[{"href":"https:\/\/m365jp.net\/index.php\/wp-json\/wp\/v2\/media?parent=14928"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/m365jp.net\/index.php\/wp-json\/wp\/v2\/categories?post=14928"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/m365jp.net\/index.php\/wp-json\/wp\/v2\/tags?post=14928"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}