The distributed e-mail feature, also called “batched e-mail,” allows you to manage a large mailing efficiently by splitting it into multiple batches or ranges. Rendering threads running on participating machines (or on multiple processors on a single machine) take batches from the queue. They then generate and send the messages in essentially the same way as single threads do for a non-distributed mailing.
Note that you can use distributed e-mail only for mailings to registered users; you cannot use it for mailings whose recipient list includes any transient profiles. This limitation exists because distributed e-mail works with the template e-mail system’s persistence mechanism, and transient profiles are not persisted to the database. (You can, however, use distributed e-mail for anonymous profiles if you use the persistentAnonymousProfiles feature. See Tracking Guest Users for more information.)
