Diagnosis
You have only set "stakeholder-dependent" as the communication type.This may have undesired results. For example if you send an e-mail withattachments to a stakeholder who has set "SMS/Pager" as standardcommunication type, this would not be desirable as these two channelsare not technically compatible.
For this reason, the system ensures that you have to specify theavailable technical communication types. If a recipient then does nothave one of the listed standard communication types, it will beignored. Instead, the system will try to find an address for one of theother listed communication types according to the priorities.

System Response
The send process is canceled.

Procedure
Start the send process again. Make sure to select appropriatecommunication types, or change your settings in Customizing(communication types).