Microsoft is working to resolve an ongoing Exchange Online issue that has been mistakenly quarantining customers' mailboxes since Sunday.
The incident, tracked by Microsoft under EX1436407, began on July 19 and remained unresolved as of the most recent update Wednesday evening. During this time, affected Exchange Online users have been experiencing issues receiving and sending emails and accessing their calendars.
Microsoft has linked the problem to a recent infrastructure change that caused excessive memory consumption, resulting in an out-of-memory condition that triggered the incorrect mailbox quarantines.
"This issue may block some users from receiving email messages due to their mailboxes incorrectly being quarantined, and users sending email to these mailboxes may receive a Non-delivery Report (NDR)," Microsoft said.
"A recent infrastructure change caused excessive memory consumption from unexpected indexing data results in an out-of-memory condition, causing affected mailboxes to be incorrectly quarantined."
