Microsoft Outlook for Windows now allows adding file attachments to emails while offline. Rollout began in late October 2025 for Targeted Release and is generally available worldwide. Users can enable offline email and attachments in settings; emails with attachments send automatically once online. Admins manage via OWAMailboxPolicy-OfflineEnabledWin.
Applies to: Exchange Online · Microsoft 365 apps
Source: mc.merill.net — data via Merill Fernando's open archive (MIT).