Untitled

Scoping transactions and sessions in NHibernate for long running tasks
var subscribers = _session
    .QueryOver<Subscription>()
    .Where(s => !s.HasReceivedNewsletter)
    .List();

foreach (var subscriber in subscribers)
{
    SendNewsletterTo(subscriber);
    subscriber.HasReceivedNewsletter = true;
}

foreach (var subscriber in subscribers)
{
    using (var txn = _session.BeginTransaction())
    {
        try
        {
            SendNewsletterTo(subscriber);
            subscriber.HasReceivedNewsletter = true;
            txn.Commit();
        }
        catch (Exception ex)
        {
            txn.Rollback();
            // log exception, clean up any actions SendNewsletterTo has taken if needed
            // Dispose of session and start over
        }
    }
}