Why does email scale better for one-to-many communication?
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Because SMTP was designed to replicate a single message to many recipients without opening a new connection for each one.
When you send an email to 10,000 people, you're not making 10,000 separate connections. Your mail server opens a connection to each receiving server (say, Gmail, Outlook, Yahoo) and says "I have a message for these 1,000 recipients." The receiving server accepts the list, stores one copy of the message, and delivers it to all 1,000 mailboxes. One connection, one transmission, thousands of deliveries.
Compare that to SMS or push notifications. Each recipient needs a separate transmission. Send to 10,000 people, pay for 10,000 sends. Email? You pay for bandwidth to transmit the message a few dozen times (once per receiving mail server), not once per recipient. That's why you can send a newsletter to 50,000 subscribers for pennies, but texting 50,000 people costs thousands of dollars.
Chat apps and messaging platforms work differently because they're built for real-time synchronous communication. They maintain persistent connections so messages appear instantly. That's perfect for a conversation between two people or a small group. But try to broadcast a message to 50,000 people at once? The infrastructure cost explodes. You're paying to keep 50,000 connections open simultaneously, just in case someone wants to reply.
Email doesn't care if recipients are online. It doesn't wait for acknowledgment. It drops the message in the mailbox and moves on. That's why ARPANET mailing lists like SF-LOVERS (a sci-fi discussion list from 1980) worked so well with the technology of the time. One message, hundreds of recipients, no problem.
This is also why ESPs can offer such aggressive pricing for email compared to SMS platforms. Brevo charges around $25/month for 20,000 emails. Twilio charges around $0.0079 per SMS, so 20,000 texts would cost $158. The protocol design makes all the difference.
If you're choosing between email and other channels for marketing campaigns, email wins on cost and scale every time. Save SMS for time-sensitive, high-value messages (shipping updates, appointment reminders, two-factor auth). Use email for everything else.
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