For the last five days I cannot send mail using Office 365. This is very frustrating and causing me to lose business. I'm on a cruise ship in the south of France and inbound mail is not a problem. I have to resort to Webmail which is very inconvenient as my Contact List is in Outlook.
The message I get is:
Send test email message: The operation timed out waiting for a response from the sending (SMTP) server. If you continue to receive this message, contact your server administrator or Internet service provider (ISP).
In my experience, you should not be using SMTP for Office 365 email. If you are using the Outlook mail client, it should support native Exchange rather than POP3/IMAP and SMTP. Here is an article that describes how to set up Outlook properly with Office 365: