Manually create a DristibuteCampaignActivityRequest - wrong sender

Hi!

I've read the code on https://msdn.microsoft.com/en-us/library/hh547397.aspx but not happy with my solution. 

I manually create a DistributeCampaignActivityRequest in a consoleApplication

Here are some codesnippets (sender is a systemuser or a queue)

Entity emptyMail = new Entity("email");
emptyMail.Attributes["from"] = new Entity("activityparty") { Attributes = new AttributeCollection { {"partyid", sender } } };

activityRequest = new DistributeCampaignActivityRequest {
							Activity = emptyMail,
							TemplateId = emailTemplateId,
							CampaignActivityId = campaignActivity.Id,
							Owner = new EntityReference("systemuser", currentUser.UserId),
							//OwnershipOptions = PropagationOwnershipOptions.Caller,
							PostWorkflowEvent = true,
							Propagate = true,
							SendEmail = true,
						};
var distributeResponse = (DistributeCampaignActivityResponse)_client.Execute(activityRequest);

The email will be created and sent, but.... the sender is the user of the connectionString and not the one set as Attribute "from" in the email-Entity.

I've tried a lot of things but no chance. If I set the callerId of the serviceProxy:

_client.OrganizationServiceProxy.CallerId = sender.id

It's o.k. but this is only possible if the sender is a systemuser. 

What else I've tried:
- set owner of the request to sender (systemuser or queue)

- set the from of e-mail in this way:

emptyMail.Attributes.Add("from", new EntityCollection());
(emptyMail.Attributes["from"] as EntityCollection).Entities.Add(new Entity("activityparty"));
((emptyMail["from"] as EntityCollection)[0] as Entity).Attributes.Add("partyid", sender);

Anybody has a solution for this?

thx a lot

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