Solus email is a term used in the email marketing industry. A solus email is a third-party advertisement that is sent to an opt-in subscription email list that is comprised of demographics of target consumers that the third party wants to advertise to.
An example of a solus email marketing would be for the owner of an opt-in list related to Internet security to allow an anti-virus software company to send a direct advertising email about their Internet security product to members of the opt-in list. The e-mail advertisement will generally not show any information about the Web site or company who owns the email list, but will appear to come directly to you from the third party brand.
Solus e-mail marketing is also called direct e-mail marketing.
See also piggyback email.