If messages are taking longer than 5 minutes to arrive in the recipient's Inbox, the delay might be happening due to a problem ...

If messages are taking longer than 5 minutes to arrive in the recipient's Inbox, the delay might be happening due to a problem with their email client. For help fixing Outlook connection problems, download Support and Recovery Assistant for Office 365

To see the full log of how Office 365 processed your message, use Message Trace.

Contacting support won't solve this issue if it�s due to a problem that's happening outside the Office 365 service.