Two-Way SMS for Customer Conversations & Inbox Replies
Two-way (replies enabled) SMS lets customers respond to your short codes, keywords, and virtual numbers so support and sales stay in one thread.
Two Way SMS
Two-way SMS is used by businesses around the world to engage with their customers. These businesses want feedback from their customers, or message recipients, based on the content they are sending. Why? Because the responses or replies come straight into their Send99 account and are incredibly relevant to the short and important messages being sent.
How two-way SMS works
Two-way SMS lets a recipient reply to your message instead of receiving a one-way broadcast. The reply travels through the mobile network to the number or short code you sent from, then into your Send99 inbox or a webhook on your own server. That creates a conversation thread that support, sales, or operations teams can act on.
A typical flow is: you send an opt-in confirmation or appointment reminder; the customer replies YES, NO, or a free-text question; Send99 captures the reply, applies any keyword rule, and either shows it in the inbox or forwards it to your application. Delivery reports and inbound-message records give you an auditable timeline.
Keywords, short codes, and virtual numbers
The reply path depends on the number type. Short codes are designed for high-volume campaigns and keyword opt-ins; long codes and 10DLC numbers support conversational replies and are common in the USA; virtual numbers give international teams a local-looking entry point. Alphanumeric sender IDs are usually one-way because recipients cannot reply to a name.
Keywords such as STOP, HELP, YES, or JOIN can be handled automatically. Map each keyword to an action, keep the responses short and clear, and make sure opt-out keywords are processed even outside business hours. If your programme uses multiple countries, confirm which number types support replies in each destination before launch.
Inbox, routing, and automation
Replies can be handled in the Send99 inbox, retrieved through the API, or pushed to your own endpoint. Route by keyword, number, or campaign so the right team sees the right conversation. A support reply should not land in a marketing queue, and an opt-out should update every system that might message the contact again.
Automation is useful for acknowledgements, office-hours responses, and simple qualification flows. Keep a human escalation path for complaints, billing questions, and anything sensitive. Log the full thread, including timestamps, so you can investigate disputes and improve response times. See the API documentation for inbound-message retrieval.
Two-way SMS use cases and best practices
Common programmes include appointment confirmations, delivery rescheduling, customer support triage, surveys, event check-in, and opt-in management. The strongest use cases have a clear next step: confirm, reschedule, cancel, or ask for help. Avoid open-ended "reply anything" campaigns unless you have staff or automation ready to handle the volume.
Tell recipients what a reply costs if your market requires it, honour quiet hours, and respond within the window you promise. Keep consent records for the original opt-in and for any keyword-based subscription. For regulated industries, review the content and retention rules before enabling free-text replies.
Frequently asked questions
What is two-way SMS?
Two-way SMS is messaging that allows the recipient to reply. Instead of a one-way broadcast, replies return to a number, short code, or virtual number and can be routed to an inbox, webhook, or application. It is used for confirmations, support, surveys, and opt-in management.
How do replies reach my team?
Replies can appear in the Send99 inbox, be retrieved through the API, or be forwarded to a webhook on your own server. You can route by keyword, sender number, or campaign so support, sales, and operations see the conversations they own.
Do I need a short code for two-way SMS?
Not always. Short codes are strong for high-volume keyword campaigns, but long codes, 10DLC numbers, and virtual numbers can also support replies depending on the country and use case. Alphanumeric sender IDs are generally one-way. Confirm the available reply path for each destination before launch.
Can I automate replies and opt-outs?
Yes. Keywords such as STOP, HELP, YES, or JOIN can trigger automatic responses and actions. Opt-outs should be processed immediately and propagated to your CRM. Keep a human escalation path for complaints or sensitive conversations, and log the thread for auditability.
How is two-way SMS priced?
You pay for outbound messages and, depending on the route and number type, for inbound messages or the number itself. Short codes and dedicated virtual numbers usually carry a separate lease or setup cost. Ask for a quote that includes both directions and any registration fees for your destinations.
Is two-way SMS compliant?
The same consent and opt-out rules apply, with extra care around free-text replies that may contain personal data. Tell recipients how to opt out, honour STOP requests, retain consent records, and follow local rules for recording and retention. Our country pages summarise the main requirements.