Configure ISA 2006 to force client to flushdns upon VPN connection?

We are having a strange issue that appears to be caused with our split-dns setup. When users connect to the ISA VPN, they maintain the old address in local cache, at least for a bit. This is causing mail connection issues, since that IP uses private internally, and public externally.

I thought when VPN clients connect to ISA they automatically flush the local dns cache, but this issue is apparently highlighting that not to be the case. Is there anything I can check to determine if it is working, or if not, to force a client to simply run a script to do that? I've never forced any scripts over or after an ISA VPN connection so if that's the case I need details on how that is done.

Environment details:
ISA 2006 via Server 2003
Connecting clients are Windows XP
VPN type is PPTP, NO split-tunneling, all traffic through the tunnel
Mail server type is Exchange 2010 (recently changed from 2007)
DNS hosted on Server 2008, split internally (private addressing) versus externally (public addressing hosted on different servers)
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Keith AlabasterEnterprise ArchitectCommented:
I'm not understanding why you would need to. If the VPN has been created then users would still see the internal IP addresses as valid - can you explain further?

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skpruettAuthor Commented:
Keith I'm going to award points to you, but it turns out this was not an ISA issue, rather it's a problem with Exchange 2010 and we are pursuing it that way instead. ISA continues to work fine to other hosts with split dns-resolution.

Thank you anyway, sir.
skpruettAuthor Commented:
Exchange 2010 appears to have some issues remotely that are happening due to other factors.
Keith AlabasterEnterprise ArchitectCommented:
More than welcome - if you need to come back to this one, just post.

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