Unblocking contact on Hotmail who isn’t actually blocked

When I send mail to a couple of my contacts they appear in the sent box with the contact blocked symbol next to them and they don’t actually get delivered either but these people have never been blocked and when I click on their names on the email it gives me their details and they are not blocked there either.
Any ideas?

Could you have blocked an entire domain? Can you block and unblock them?

How do I block a domain? I’m not good with this sort of thing so could have done.

What are you using to send emails – an app or the web client? If the former, it may be the server end that is doing the blocking which may not show up in your email client.

I would log in using the Outlook web client and check your Junk email settings there – there are options for safe and blocked emails and domains. Check they are not under the blocked settings (remove if they are) and, if not, try adding them to the safe list.