If you are sending marketing messages to consumers by email, there are certain restrictions on what can be sent and to whom. In the first instance, there is an important distinction to be made between ‘individual’ and ‘corporate’ subscribers. Individuals have private email addresses, such as email@example.com, whereas a corporate subscriber could be firstname.lastname@example.org.
In terms of individual subscribers, your business should not be sending messages to anyone without their permission. The exception to this is if you have obtained the person’s details as a result of an earlier sale, or during negotiations concerning a sale, and the messages you are sending are about related or similar products or services to those sold or discussed previously. If you are sending emails in this way, you must have given recipients an opportunity to opt out of receiving these kinds of communications beforehand. If you are emailing a business, the requirement for prior consent does not apply.
Strictly speaking, there is no prohibition on sending marketing emails to businesses, but it is important that your emails are not perceived as spam. Communications must identify the sender organisation and be clearly identifiable as being for marketing purposes. Whilst the best subject headers make bold, eye-catching statements, these must be distinguished from misleading or false advertising claims.
If someone on your mailing list wishes to unsubscribe and stop receiving communications from you in the future, this must be a simple process. If it is not, and other methods of contact or complaint prove futile, your organisation could be investigated by the Information Commissioner, who has the power, in the most serious cases, to order you to change your business practices.