Hi,
support for older versions of DP in higher versions is limited to the Disk-Agent only. And it is not supported for integrations like Exchange.
The old 6.20 bits (end of support in April) can be downloaded from SSO (support.openview.hp.com) and will be provided if you have a valid systemhandle (your software under support). When downloaded, you are able to install DA only in your DP 7 cell. You can try to use the ESE integration as well, but there is no guarantee that this is working.
Best regards
Daniel