Send Port in Orchestration a must?

Hi.

A short question to orchestrations.

Do I always have  to use a send port in an orchestration?

Because if I don’t use a send port in an orchestration I get always an error message like this:
“
xlang/s engine event log entry: Uncaught exception (see the ‘inner exception’ below) has suspended an instance of service ‘MPDB2PB.MPDB2COM_Assembly(99b80d62-c27d-be09-86d8-ce55ccc7c9df)’.

The service instance will remain suspended until administratively resumed or terminated.
If resumed the instance will continue from its last persisted state and may re-throw the same unexpected exception.
InstanceId: 0a934683-2d8c-4e67-ac02-24f58156124f
Shape name: Send_1
ShapeId: 36f773bc-d1cf-4de1-84c1-10b70f3994fc
Exception thrown from: segment 1, progress 11
Inner exception: Failed while attempting to send message ‘RcvDataFromMPDB’.
 
Exception type: SendFailedException
Source: Microsoft.XLANGs.BizTalk.Engine
Target Site: Void WriteMessageState(Microsoft.BizTalk.Interop.IBTPEPInfoLookup, System.Guid, Microsoft.XLANGs.BaseTypes.XLANGMessage, Microsoft.XLANGs.Core.Segment, System.String, System.String, System.Collections.IList, Boolean, System.Collections.IList)
The following is a stack trace that identifies the location where the exception occured”

In the orchestration I have a receive port and an expression shape only.

I’m a little bit confused because I heared that it shouldn’t be a problem for BizTalk if I don’t use a send port in an orchestration.

If included a send port the orchestration is running fine without any issues.

So I think I have to use a send port within an orhcestration, or am I wrong?

What are your experiences in this or does this depends on the shapes in an orchestration?

Thanks in advanced.

Wolfgang