Unique code sets can be distributed to existing subscribers as part of your email strategy.
Seguno users
Unique codes can be used in emails and automations in Seguno: Email Marketing. Seguno will send a unique code to each subscriber and track the sales by discount set and individual discount codes.
Other email providers
To send unique discount codes to subscribers through different email providers, export the discount codes to a CSV file. Reference your email provider's documentation on importing data into a contact field to insert the codes into an email.