Intermittent M365 Add-in Timeouts

Proofpoint has received reports of the M365 Add-in timing out. After investigation, it timeouts while attempting to download the Office-js code required for any Microsoft Add-in to run. The reason for this is because the TLS certificate for ajax.microsoft.com: http://ajax.microsoft.com/ expired earlier today, Saturday, January 10, 2026 at 12:50:49 PM As soon as Microsoft updates their certificate, Office Add-ins functionality will return to normal. Customers on the newer Smart Alerts version of the M365 Add-in will fail open if configured to do so. Customers on the classic version of the M365 Add-in will fail closed, and users will not be able send email. Customers on Smart Alerts using Classic Outlook on Windows are not impacted at all. Some users may not be impacted, as their Outlook client still has a valid certificate cached. We will update this issue when Microsoft updates their certificate.