From Field

The email you put in the FROM field does not need to be a live address, but it does need to be from your domain. For example:

From: [your-name] <wordpress@your-domain.com>

It doesn’t “need” to be from your domain, the form will still work. It’s just an annoying error message that shows on the dashboard. They should remove the error message, or at least tame it, unless they have a good specific reason for it. As it is this is terrible UX.

The reason is to prevent email forgery, whereby the email is sent from one domain, but claims to be from another (e.g. paypal.com):

Forged emails appear to be sent from a legitimate Yahoo email address even though they aren’t, and are used to spread spam and other types of malicious phishing scams. It’s very difficult for the average user to recognize the difference between a legitimate email and a forged one.

To receive responses with an “@yahoo.com” address, either a Reply-To: header or email forwarding from authoritative domains are the suggested options. Bounces should also be managed within your authoritative domains.

Yahoo help

End users and companies all suffer from the high volume of spam and phishing on the Internet. Over the years several methods have been introduced to try and identify when mail from (for example) IRS.GOV really is, or really isn’t coming from the IRS

dmark.org

@barnez +1

That’s a pretty fair reason tbh.

The curse of spam. I’m going to miss not having the sender’s email in the From column of my mail client.