The General Purpose Process global change is responsible for processing bulk jobs submitted by BBNC among other consumers. The job will pull data from the NC tables, package it together in chunks and submit it to ShelbyServices.
There are three global changes related to Email Services (Infinity platform feature) that are responsible for processing email jobs, listed below:

General Purpose Email Poll
-processes bulk jobs (eCampaigns, eBlasts, Fundraiser blasts, notifications etc.)

Transactional Email Poll
-process trx jobs such as acknowledgements from NC

Email Status Poll
-Retrieve job status information from ShelbyServices