如何在Task.WaitAll中避免死锁

Question

我在Console应用程序中有多个正在运行的任务。在我的任务中，我从EWS Managed API调用了一些方法。所以当EWS抛出异常代码执行时不会返回WaitAll。

while (index < messageData.Count)
{
    var mess = messageData[index];

    var task = new System.Threading.Tasks.Task<EventsCreationResult>(() =>
    {
        EventsCreationResult taskResult = null;
        taskResult = CreateEmail(mess, Service);
        return taskResult;
    });

    task.Start();

    tasks.Add(task);

    index = index + 1;
}

System.Threading.Tasks.Task.WaitAll(tasks.ToArray());

和功能

public static EventsCreationResult CreateEmail(string folderName, EmailMessage mess)
{
    EventsCreationResult result = new EventsCreationResult();
    result.Key = mess.Subject;

    try
    {
        mess.Save(FindFolder(folderName).Id);
        result.EventsCreationLog = "Message created:" + mess.Subject;
    }
    catch (Exception ex)
    {
        result.Error = ex;
    }

    return result;
}

那么如何避免死锁，如果它可能不会取消不会引起错误的任务。