Our company is using Outlook.com with our own custom domain, set up with the appropriate MX records on our web host. My colleague occasionally has trouble sending me e-mails, usually a reply or forward. They will come back to him with a bounce message.

However, today he forwarded me a message. As far as he could tell, the message sent OK, with no error message being returned to him. I never received the e-mail, not in my Inbox or Junk Mail folders.

I reviewed the article "I'm not receiving emails sent by my family or friends". Of its suggestions, the only one not in place already was adding my colleague to my contact list. However, it should not be necessary to have someone in my contact list in order to receive an e-mail from them, in the junk mail at the very least.

This is a serious issue, as we cannot operate with e-mails not being delivered without warning.