New exchange and AD setup question

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I am migrating a NT4 domain to 2003 and adding a new Exchange serveur to
replace MSMAIL.
I have a registered public domain (i.e company.com) that is hosted by my ISP
that offers us POP3 account and resolves the www.company.com address to an
outside public address.

I would like to have the ability to create within Exchange our own public
email addresses so we would manage the mailboxes@xxxxxxxxxxx

What would be my approach for the setup of AD/DNS/Exchange to permit
internal mail, internet mail and correct resolving of company.com domain.

Thank you

Sebastian


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