email cast error in plugin?

Hello - I'm trying to get a handle to the email entity in the Email post-save plugin.

The following code *was* working at 1 point because the plugin was able to complete and save:

if (context.InputParameters.Contains("Target") && context.InputParameters["Target"] is Entity)
{
// obtain the target entity from the input parameters
var email = (Email)context.InputParameters["Target"];

However, now the last line is returning the following error:

"Unable to cast object of type 'Microsoft.Xrm.Sdk.Entity' to type 'MyGennedEntities.Email'"

I also tried using the following code in the last line:

var email = ((Entity)context.InputParameters["Target"]).ToEntity<Email>();

However, this code returns the following error at runtime:

"Unable to cast object of type 'Microsoft.Xrm.Sdk.Entity' to type 'MyGennedEntities.ActivityParty'"

Any idea what I'm doing wrong here, what might be going wrong, how to fix or debug?