Hi Anuj,
Based on my knowledge, there is no official article to explain whether .NET framework 3.5 SP1 is supported on Exchange 2007 SP1. But .NET framework 3.5 SP1 is supported on Exchange 2007 SP3.
What's more, you need to install .NET framework on all Exchange server roles.
For more information, here is an article for your reference.
Exchange Server Supportability Matrix
http://technet.microsoft.com/en-us/library/ff728623(v=exchg.150).aspx
Hope it helps.
Best regards,
Amy
Amy Wang
TechNet Community Support
