User impact: Users’ OME email messages sent through Exchange Online couldn’t be opened by some recipients.

More info: This issue prevented recipients that use third-party email clients from opening the encrypted email messages. The recipient may have received the OME email messages but attempts to open the message were met with continuous loading prompts.

Final status: We’ve completed the redeployment of the recent Exchange Online update and confirmed with affected users that impact is remediated. Some users will need to clear their browser’s cache before they are able to access OME email messages.

Scope of impact: Impact was specific to users sending OME email messages who were served through the affected infrastructure and their recipients that used third-party email clients.

Start time: Thursday, April 27, 2023, at 5:00 AM UTC

End time: Thursday, April 27, 2023, at 1:55 PM UTC

Root cause: A recent update to Exchange Online wasn’t properly deployed to the affected environment and was missing some scripts necessary to facilitate access to encrypted email, resulting in impact.

Next steps:
– We’re reviewing the infrastructure responsible for deploying updates to Exchange Online to identify where the failure occurred within the deployment process, allowing us to prevent similar impact in the future.

This is the final update for the event.