SMS vs WhatsApp vs Email in India

Founders building customer communications for India inevitably ask whether they should be sending SMS, WhatsApp messages, or email. The honest answer is "it depends on the job." Each channel has a different shape — different cost, different latency, different compliance — and the right call depends on what you're trying to achieve. Here is a practical breakdown.

The numbers that actually matter

Channel	Open rate	Cost / message	Time to delivery
SMS (transactional)	~95%	₹0.18–0.30	~2–10 sec
SMS (promotional)	~90%	₹0.12–0.20	~5–30 sec
WhatsApp (utility)	~95%	₹0.16/conversation	<3 sec
WhatsApp (marketing)	~85%	₹0.78/conversation	<3 sec
Email (transactional)	~30–45%	₹0.05–0.10	~5–60 sec
Email (promotional)	~15–30%	₹0.05–0.10	~30 sec–2 min

These are 2026 production numbers we have seen across actual Indian SMB and consumer accounts. Your mileage will vary by industry, list quality, and time of day.

Where SMS still wins

OTPs. Sub-second delivery, works on every phone including feature phones, no app required. WhatsApp OTP is cheaper but doesn't reach users without the WhatsApp app.
Critical alerts where reach is non-negotiable. "Your appointment is in 1 hour" to a 65-year-old patient. SMS has the highest reach floor of any channel.
Short, one-way notifications where opening a chat would be overkill. Order shipped, payment received, account locked.

The Indian compliance layer (DLT registration, sender ID approvals, TRAI guidelines) makes SMS more bureaucratic to set up than email or WhatsApp — but once set up it is the most reliable channel for transactional one-shot messages.

Where WhatsApp wins

Two-way conversations. Customer replies, agent answers, all in one thread. No other channel does this naturally.
Rich media. Product images, PDFs, video, location, payment buttons. SMS is plain text only; email is rich but not as widely read.
Order journey messaging. Confirmation → shipped → out for delivery → delivered. Each step a separate message, each one expected by the customer, all open rates above 90%.
Re-engagement. Cart abandonment nudges, re-stock notifications. Far more likely to be seen than email.

WhatsApp's main constraint: opt-in. You must have explicit consent (collected through a checkbox, a "send me updates on WhatsApp" prompt, or an existing transaction). Sending unsolicited WhatsApp messages will get your number throttled and eventually banned.

Where email still wins

Long-form content. Newsletters, case studies, post-purchase thank-yous with detailed instructions. SMS and WhatsApp are not the right format for 500 words of useful context.
B2B communication. Decision-makers spend their workday in inboxes. WhatsApp B2B is growing but not dominant; email remains the default channel.
Receipts and invoices. Permanent, searchable, easy to file. WhatsApp can deliver them but emails are still preferred for accounting.
Cold outbound. Email is the only channel where compliant cold outbound is legal at any scale. SMS and WhatsApp without consent will get you blacklisted.

The downside: open rates are an order of magnitude lower than SMS or WhatsApp. The upside: cost is also an order of magnitude lower, so the unit economics balance out for high-volume use cases.

The job-to-channel map

OTP / 2FA: SMS (with WhatsApp as a cheaper fallback for users with WhatsApp).
Order confirmation and shipping: WhatsApp first, SMS as fallback for non-WhatsApp users.
Promotional offers: WhatsApp (if you have opt-in), email as the volume channel.
Newsletters and product education: Email.
Customer support: WhatsApp for fastest response; email for issues that need history and attachments.
Cart abandonment: WhatsApp at the 1-hour mark, email at 24 hours.
Reactivation campaigns: Email primary; WhatsApp only if customer has been recently active.
B2B outreach: Email (cold) or LinkedIn (warm).

The compliance landscape

SMS: DLT registration with one of the four telecom-approved DLT platforms is mandatory. Sender ID and template registration take 1–2 weeks. Promotional SMS to numbers on DND lists is illegal.
WhatsApp: Opt-in required. Templates must be pre-approved. Marketing templates are subject to per-user opt-out.
Email: CAN-SPAM (US) and GDPR (EU) apply for international audiences. India's DPDP Act has light email-specific rules but explicit consent is still good practice.

The honest summary

You don't pick one channel — you pick the right one for each job. A working B2C messaging stack in India looks like SMS for OTPs, WhatsApp for transactional and conversational, and email for newsletters and B2B. The tools to manage all three through a single API are mature: most BSPs (we partner with several at eDarpan's SMS service and WhatsApp Business service) offer unified inboxes that cover all channels.

The wrong move is to send the same message on all three channels. The right move is to send the right message on the right channel — once.