Any sender can forge any From address they wish when sending an email. Spammers often use random or changing From addresses or spoof the good addresses of others. For example, I own a personal domain and from time to time spammers will send spam forging an address at my domain in the From field. Responses then come back to me instead of the spammer.
So blocking random spam based on the From address is of limited use. It only works if someone repeatedly sends you messages with the same From address or a domain you are willing to block.
Outlook consists of both the online outlook.com email provider and the Outlook local email client.The Outlook local email client can block an email address or a domain. If right-clicking a spam email and selecting
Junk>Block Sender does not work for some reason, instead select
Junk>Junk Email Options and select the
Blocked Senders tab, where you can add an email address or a domain.
You also need to consider that there are two completely different From and To addresses which are used when an email arrives for you at your email provider:
- Envelope addresses: These are used to transport the message to your account, and to communicate connection problems to the sender.
- Normal header From, To, and Cc addresses: These are what you normally see in an email client. They can contain anything, and in general do not have to be related to the envelope addresses. Typically a message can have pretty much anything (or nothing) in these headers, since they are not used to transport the message to your account.
So if the normal From header address is missing or not properly formed, the message will probably get to you just fine (if the spam filter doesn't catch it). But Outlook may not have anything to use for blocking if the From field is missing or badly malformed. It's also common for spam senders to place your email address in both the From and To headers. This is easy to do, and is not blocked by the email transport system which places the email in your account. Some spam filters may catch this and block such a message with From == To.
Bill