Microsoft is working to fix an Exchange Online service outage that intermittently prevents users from accessing their mailboxes via the Internet Mailbox Access Protocol 4 (IMAP4).
The incident (tracked under EX1215307) was first acknowledged on Wednesday at 23:35 UTC, with Microsoft noting that other connection methods are not affected and advising those impacted that retries may help regain access to their emails.
Microsoft says it already deployed a fix to address these ongoing issues, which are caused by a code conflict that introduced an authentication misconfiguration.
“A recent IMAP deployment related to authentication support contains a code conflict that introduced a configuration issue and is causing intermittent mailbox access issues for some impacted users,” Microsoft said.
“We’re continuing to deploy the configuration change and expect this process to complete by our next scheduled update.”
While Microsoft has yet to detail what regions and how many users are impacted by this ongoing IMAP4 access issue, it has been classified as an incident in the Microsoft 365 admin center, a flag usually applied to critical service issues with noticeable user impact.
Microsoft mitigated a similar Exchange Online outage in November that blocked customers’ access to mailboxes using the classic Outlook desktop client.
The November incident followed a major DNS outage in late October that impacted Azure and Microsoft 365 services, preventing users from logging into company networks and accessing multiple services and platforms.
Several weeks earlier, in early October, Microsoft addressed another outage blocking customers from accessing Microsoft Teams, Exchange Online, and the admin center via Microsoft Entra single sign-on (SSO) authentication due to Multi-Factor Authentication (MFA) issues.
This week, Microsoft has canceled plans announced in April 2024 to enforce a daily limit of 2,000 external recipients on Exchange Online bulk email senders.
This is a developing story…
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