Bulk email software is software that is used to send email in large quantities.
It might be used for legitimate mailings - for email list subscribers. Since the bulk email software usually sends email via direct send and via SMTP server the use of a bulk email software for spam is almost impossible, because of the large amount of emails that are sent in a spam campaign.
Bulk email software usually refers to a standalone software, while there are bulk email sending web based services as well.
