Microsoft Exchange Outage Blocks IMAP4 Mailbox Access
▼ Summary
– Microsoft is fixing an Exchange Online outage preventing intermittent IMAP4 mailbox access, having deployed a fix for an authentication misconfiguration caused by a code conflict.
– The incident began on January 1st, with Microsoft advising impacted users that retrying may help and noting other connection methods are unaffected.
– Microsoft has classified this as an incident, indicating a critical service issue, but has not detailed the impacted regions or number of users.
– This follows several recent Microsoft service outages, including ones in November and October affecting Exchange Online, Azure, Microsoft 365, and Teams.
– Microsoft has also canceled a previously announced plan to enforce a daily 2,000-recipient limit for Exchange Online bulk email senders.
Microsoft is currently addressing a service disruption within Exchange Online that is intermittently preventing users from accessing their mailboxes through the Internet Mail Access Protocol version 4 (IMAP4). The company has identified the root cause and is implementing a fix, though some customers may still experience sporadic connectivity problems.
The incident, which Microsoft is tracking under reference EX1215307, started on January 1st at 19:00 UTC. According to official communications, other methods for connecting to Exchange Online, such as Outlook on the web or modern authentication clients, remain unaffected. Users who encounter access problems are advised that simply retrying the connection may temporarily resolve the issue.
Microsoft engineers have traced the problem to a code conflict within a recent IMAP deployment. This conflict created an authentication misconfiguration, leading to the intermittent access failures for a subset of users. The company stated, “We’re continuing to deploy the configuration change and expect this process to complete by our next scheduled update.”
While Microsoft has not provided specific numbers or a detailed geographic breakdown of affected users, the problem has been formally classified as an incident within the Microsoft 365 admin center. This designation is typically reserved for service issues that have a significant and noticeable impact on customers.
This is not the first such disruption for Exchange Online in recent months. In November, Microsoft resolved a separate outage that blocked access for users of the classic Outlook desktop client. That incident followed a major DNS outage in late October that impacted a wide range of Azure and Microsoft 365 services, disrupting logins and access to numerous platforms.
Further back in early October, the company addressed another widespread issue that prevented access to Microsoft Teams, Exchange Online, and the admin center. That outage was linked to problems with Multi-Factor Authentication (MFA) through Microsoft Entra single sign-on.
In related news, Microsoft has recently reversed a policy change announced in April 2024. The company will not proceed with plans to enforce a daily limit of 2,000 external recipients for Exchange Online bulk email senders.
Update: As of January 08, 10:48 EST, Microsoft has confirmed the issue is resolved. A configuration change deployed across all affected servers has successfully “reduced volume and restored normal service functionality.”
(Source: Bleeping Computer)
