Transactional SMS and promotional SMS belong to the same category bulk SMS.
However, they are used for different purposes.
Transactional SMS is used to send order and booking notifications, financial alerts such as banking alerts, ATM transaction details, checkbook disbursal messages, account status, etc.
This type of messages can also be used to send confirmation messages such as airline booking, rail booking, courier booking, etc.
Transactional SMS can be sent to do not disturb numbers otherwise known as DND.
As per the telecom regulations, transactional SMS has the provision to reach any numbers, whether DND or non-DND, due to the nature of the messages delivered.
Promotional SMS is a pure marketing and sales tool.
These messages are sent to your existing customers, new customers, and opted-in customers but not to the DND numbers.
These messages may not be solicited by the customers when compared to the transactional messages where the customers have a purpose to receive the messages.
Promotional messages are used in marketing campaigns, branding, to promote discounts and offers on your products, launching of new products, and advertise a service or product.
These are very effective for marketing especially if you are a new, or a start-up company.
Both transactional messages and promotional messages are useful to organizations based on their purpose of sending these messages.
While both service different categories, both have a rapid reach and high open-rate.