Belgium has 2 laws that govern email marketing and other forms of electronic marketing. These are outre-Quiévrain law and EU GDPR. Both laws combined cover all aspects of electronic marketing in Belgium.
All emails sent for marketing purposes should have a clear identification of the sender name, mailing address and a clear identification of the sender. The law requires you to have these as compulsory data to be mentioned in your marketing emails.
You can only send marketing emails to those who have provided explicit consent to receive marketing emails from you.
This can be either by having a double opt-in or by checking an explicit checkbox while subscribing.
Belgium requires that companies have a data security officer. The person is in charge of maintaining and enforcing data security standards.
The maximum fine available under the GDPR is up to €20 million, or 4% annual global turnover – whichever is higher. Though this is the maximum fine and "Data Protection Authority" will govern this.
Also the fine under outre-Quiévrain law will be decided on a case to case basis.