The best SMS marketing software for marketing agencies
An agency's problem is not sending a text — it is sending texts for fifteen clients without fifteen logins, fifteen cards and fifteen compliance headaches. The platforms that win a brand do not automatically win an agency. We ranked six on how well they handle a roster: sub-accounts, API automation, and whether you can make margin on the resale.
We reweighted hard toward multi-client operations. The best single-brand SMS tool is the wrong answer if every new client means a new account, a new invoice and a new place for something to go wrong. See the full rubric →
Multi-client management30%
API & automation20%
Deliverability & 10DLC20%
Value & margin15%
Ease of use15%
01
RANK
★ Editor’s Choice
SimpleTexting
Best multi-client control
SimpleTexting hits the agency sweet spot: clean multi-user access, a real API, predictable credit pricing you can mark up, and it works for any vertical — not just ecommerce. It is not the cheapest per client, but it is the one you can actually run a book of business on without fighting the tool.
If your clients are Shopify DTC brands, Klaviyo is the most powerful play — SMS and email on one profile, deep store data. The catch for an agency: it is built around a single brand's store, so a mixed roster of local and service clients makes it the wrong centre of gravity.
Sakari is the most genuinely agency-shaped tool here: strong API, multi-account structure and partner programs aimed squarely at resellers. It asks more of you technically than SimpleTexting, but if you are automating across many clients it pays that back.
EZ Texting is an easy, inexpensive way to stand up SMS for a small client fast. It is shallower on true sub-account isolation and API depth, so it is better for a handful of simple clients than a scaling agency book.
No monthly subscription, just per-message pricing — useful when client volumes are spiky and you want costs to track usage exactly. The flip side is no real multi-tenant structure, so you manage separation yourself.
Postscript is superb — for Shopify. That is exactly the trap. An agency that standardises on Postscript or Attentive quietly bets its whole book on ecommerce clients and prices out the local and service businesses that make up most agency rosters.
Sub-accounts so each client is isolated, one login to manage them all, billing you can consolidate and re-mark-up, and an API to automate onboarding and sends. Without those, every new client multiplies your admin instead of your revenue.
Can I white-label SMS for clients?
Partly. Sakari and SimpleTexting come closest with reseller and multi-account structures; most others expect you to operate per-brand. True end-to-end white-label is rare, so confirm exactly what is rebrandable before you promise a client.
Klaviyo or SimpleTexting for an agency?
Klaviyo if every client is an ecommerce brand on Shopify and you want SMS plus email on one profile. SimpleTexting if your roster is mixed — local services, B2B, events — because it is not tied to a store and you can run any vertical on it.
Do I handle 10DLC compliance per client?
Yes. In the US each client's brand and campaign must be registered for 10DLC, and carriers police it. Pick a platform that walks you through registration per sub-account; treating it as optional gets messages throttled or blocked.