Aspose.Network for .NET v4.0.0.0 comes with .NET framework 3.5 supports.

Moreover, we also improved the Tnef attachment files decoding in this release. You don’t need to care about the Tnef attachments (winmail.dat) in the eml files now. Just use MailMessage to load the file, we will decode the tnef file for you in the background.

Check it out