This question is based on the answers provided above. The question is not how and why to authenticate server mails from same domain which makes it different, I want to know when it is appropriate to do so!
The security risk:
PersonA@samecompany.com can send a mail to
PersonB@samecompany.com and fake the
From: adress to
Now obviously the ip adress is logged and the person who faked the mail can be made responsible but maybe only after the damage has been done.
I would guess there is no need for a domain which is used by a single person or a very small group of people to authenticate the
From part. But when is it appropriate? Should a very large company check if
PersonA is really
PersonA and not
PersonC despite they are using the same domain