I'm getting a variety of spam that's one email address sent on behalf of another. The first email address seems to be one of a small group of domains e.g. mcsv.net, which I'm guessing is some message sending service.
I've added these as blocked domains in junk email, yet I still get emails.
I'm guessing that Outlook's junk mail filter may be ignoring the first email, but just curious if anyone knows for sure why this is happening.