Placement of mail server (is mail relay server needed?)

Heres my planned network

I bought the domain name through NameSecure. Instead of using their DNS servers, I plan to use my own DNS server (as shown in picture).  so I will be hosting a website, and I will have an exchange server here.

The mail server is for internal clients. When they are outside of the facility, they will use https://owa  to access their mail.
Did I set everything up correctly? Should the mail server be placed internal? Or does it stay in the DMZ?   (im kind of confused on the placement of the mail server)

Thanks in advance
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Just my opinion, but since the Exchange server is so dependent on the AD services, it makes more sense to keep it on the local LAN and only forward smtp and https to it.
If you want to take your security one step further, then put a basic SMTP relay box in the DMZ, perhaps something with a spam filter in it, like Ironmail or something. If your firewall is a PIX, then this will allow you to keep the smtp fixup enabled (you must disable it for Exchange), and keeps you from having any direct outside-inside access to your Exchange server.

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dissolvedAuthor Commented:
thanks, all i needed to know. Your answers are to the point, and easy to understand.
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