security for Exchange push email

I have set up my exchange server to push email to mobile clients, to do this I have opened port 80 on the firewall pointing to the exchange server, I have locked down ISS to only allow IP's from the mobile range.

Is there anything else I can do to improve the security?

I value the need for good security so I have awarded high points
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Matthew MillersCommented:
Here is a good article for securing client access on exchange 2003.

I would first start by getting a certificate and enabling SSL.

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Definately certificate+SSL.
Additionaly you should define a more restrictive Exchanger Activesync policy in Exchange management console (require device password!) and assign this policy to all users, and disable Activesync functionality for all users that don't need it.
jacassAuthor Commented:
Thanks for your help guys, and speed.
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