Become ™ review for Klaviyo: Email Marketing & SMS

We don't use SMS so based on my experience with Klaviyo as an EMS it is the best one out there in terms of functionality and accessibility. If you can't do what you want with Klaviyo then you can always use Integrations to add to the functionality. And if you need more functionality than that then you need to write custom software for your bespoke needs.