A bulk email is a single email sent to numerous recipients, which can be from hundreds, to thousands, to millions, and so on. Bulk emails can contain countless forms of content such as party invitations, newsletters, group messages, forwarded messages, announcements, mass emailing softwarereviews, marketing tools and tips, classified ads, and other kinds of emails. Most prominently, bulk emailing is used as a tool for email marketing campaigns which are now widely used by individuals or email marketing companies to promote their services or products.
The term bulk email is synonymous to the term mass email. It is also traditionally referred to as an email blast, figuratively referring to an explosion of emails. However, it is commonly confused with the term spam email. A spam email is any email delivered, usually for commercial purposes, without permission from the recipient. In other words, the recipients did not subscribe to the sender, or basically did not want the email at all.
On the other hand, with a good email marketing program an email can also be called an opt-in email. Unlike spam emails, opt-in emails are bulk emails sent to recipients who have specifically subscribed to the sender. This can happen when people obtain information about certain products or services they become interested in. They go to the marketer's website and willingly give away their email addresses through sign-up forms so that the marketer can send them emails about the products or services from time to time. In this case permission was given to senders to send the emails. A lot people do this in the course of the process and soon there will be a list of recipients to which bulk emails are to be sent; whereas spam emails are simply sent to many non-specific recipients. Opt-in email recipients want to receive the emails being sent to them, while spam email recipients do not. That is the most distinct difference.