How do I block emails from "no sender"?

This workaround might work. Use a browser to sign in to your outlook web app. Click Settings - View all Outlook settings - Mail - Rules. Add a new rule:

1. Give it a name "blank sender" or whatever you want to call it.

2. Condition: Apply to all messages

3. Action: delete

4. Click Add an exception (optional): Sender address includes @

That might take care of all spammers with blank address. Keep in mind that they can change their tactics to beat your rule.

Great idea but it will not let me do that. I have to give an actual email address, not just @. Thanks.

I guess I didn't state my dilemma clearly. I would like these emails deleted so that I don't need to go through them to decide that they are from unknown senders.

Eine Regel erstellen das der Absender gelöscht wird oder uf dem Server in die Blacklist setzen

LG Alex

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Das Problem ist, dass dies nicht ohne die Angabe einer E-Mail-Adresse möglich ist, aber trotzdem danke.

Great idea but it will not let me do that. I have to give an actual email address, not just @. Thanks.

Perhaps a snapshot can explain better:

The rule deletes ALL messages except the ones with @ sign in the sender address. All email addresses contain @ sign.

You're still not choosing an appropriate condition. The condition you want is either "message header includes" or "message body includes" and then use a string that is occurring in most of the messages, either in the body or in the headers.

For example, if you were to look at the message headers of a message by clicking the three dots at the right side, clicking View, then "View message source" you could then look for a domain in the headers you could use. In the second image I've include, you can see a "Return-Path" header with a domain of "consumerconnection-email.com" in it. You could use the string "consumerconnection" in the field specifying the string you're looking for and if it's found, the action would be Delete. Is that any clearer?

I understand you have your way. I'm an email administrator so I know how to check headers. Mail headers can be spoofed too. It's unreliable.

I posted my way to combat blank sender spam. I am not experiencing the problem of receiving spam with no email address so I can't test my rule to see if it works.