I've received notifications and newsletters from Microsoft and Facebook in the past and noticed that both emails came not from an address such as something@facebook.com or something@microsoft.com.
Not event something@somethingelse.microsoft.com but both had different domains such as :
reply@email.microsoftemail.com and something@facebookmail.com
Why is this? Any particular advantage in doing so?
Other than not polluting the employees email software, I can't see.
There are a variety of reasons:-
Ceding control of email to a local part of the business e.g. someone@pl.microsoft.com, or a different section of the company for account management reasons.
A different business controlling email i.e. outsourced situation where the company can't/don't want to cede control of their primary web domain.
Denoting different sections of the company for political, security, or business reasons i.e. staff moving intra-company get new email addresses on each occasion for security reasons (control of the old account remains with the old division and confidentiality is maintained).
Chinese walls e.g. British Telecom in the UK was forced by the regulator to split into three separate and competing businesses for a time they were forced to use the same root domain so you'd have someone@retail.bt.com. I've seen similar situations in a law firm where different teams are working for competing clients, so literal and figurative walls have to be put in place to ensure the clients business secrets remain that way.
I'm sure there are others, I've seen all of the above in practice. Beyond the corporate structure of large businesses, outsourcing of corporate functions or business confidentiality I can't see any particular advantage for smaller companies.
There is one major reason that has not been clearly mentioned, and it is SPAM-prevention.
E.g. if you register at facebook, you'll receive an email from an address like:
Facebook <register+AHkhAc21pbWt5LmMvbQ@facebookmail.com>
The main reason I think, is that especially when registering there is a high rate of wrong indicated emails etc, so a high drop-off quote. And some providers like Gmail adapt your "rating" according how other users handle emails sent from you.
So, to avoid that registration emails land in SPAM, facebook literally sends from different addresses/servers so this issue just does never exists.
This could be because they want to separate out the email that goes to and comes from the customers from their internal email. It's a similar thing to why shops have security doors separating their staff rooms and back offices from the main part of the shop.
There are different sort of concerns with those two sorts of email with regard to security, archiving, reliability, access by multiple people, automated processing etc.
