We are using one of the Out of the Box SharePoint 2010 workflows. The choices for the active parties in the workflow were made. Everything looks OK in the Workflow activity viewer, i.e. tasks were created, etc. The only problem is only one of the 4 participants received an e-mail notifcation. The Exchange admin checked the SMTP server logs and it only showed the e-mail sending to the one guy. However, there were no errors to indicate a problem with the others. They simply were not sent. This is not happing in all cases, but it a MAJOR problem as management wants to be able to depend on SharePoint to send the appropriate notifications so the participants will not have to manually look at the workflow to see if they have something scheduled to do.
Any idea where the failure may be taking place. I've asked the SharePoint Farm admin if the servers do not log the individual workflow activities to see if/why SharePoint may have failed to initiate the e-mail instructions to the SMTP server.