Using more than 1 email identity

Hello,

I just started a new job and my new group has TOO MANY emails being routed
to their personal inboxes. I want to setup additional email accounts so that
when someone in the company needs to request XYZ, they can send it to
XYZ@ABC.com. This will allow our group to better manage our emails and be
more productive. So when this new account is complete, I can expose the XYX
account in my Outlook Folder List. I thought that at my old company when we
did this and I created a new message from any of the various email accounts I
had access to, it automatically sent the email from the email account I was
in when creating the new message. Meaning if I created a new account from my
personal email account, the from that would show up in the receivers box
would say from me, and if I sent an email from the XYZ account, the from
would say XYZ in the receivers inbox. If I am correct, the IT group here
does not know how to do it. They are telling me that everytime I create an
email, I need to expose the From field while creating the new email and type
in the email address that I want the email to be sent from. Please tell me
they are wrong and how to explain to them to set the account up correctly.