Can you email a phone number? Carrier gateways and their limits

Yes, you can email a phone number, for now and only on some carriers. Send an email to 5551234567@vtext.com and a Verizon customer gets it as a text. People have used this trick for decades. They send server alerts to themselves, ping a technician from a ticketing system, or wire a contact form to someone's phone without paying for an SMS provider.

The trick holds up for personal alerts and fails for business messaging. Carrier email gateways are unregistered, unmonitored and shrinking. Carriers filter them, they give no delivery confirmation, and they skip every compliance step a business sender is now expected to take. This post covers how gateways work, where they break, when they're still fine, and what the registered alternative looks like, including the cost.

How carrier email-to-SMS gateways work

Each carrier runs, or ran, a mail server that turns an inbound email into a text. You address the email to the 10-digit number at the carrier's gateway domain. The gateway strips the email down to plain text, cuts it to fit, and hands it to the carrier's network as a message from a gateway short code or an email-looking sender.

Carriers change these without much notice, so check the carrier's current support page before you build anything on one. AT&T's shutdown is the clearest example. Any business that routed alerts through txt.att.net lost a large share of US phones overnight.

Why gateways break for business messaging

You have to know the carrier, and carriers change

The address depends on the carrier, and you usually don't know which carrier a customer uses. Customers also switch carriers and keep their numbers. A number that was on T-Mobile last year may be on Verizon now, and your email to @tmomail.net goes nowhere. A phone carrier lookup can tell you the current carrier, but you'd need to repeat it before every send to stay accurate. At that point you're doing a messaging provider's work without a messaging provider's delivery.

It's unregistered traffic, and carriers filter it

US carriers now expect business texts to travel over registered routes. On standard 10-digit numbers that means A2P 10DLC: a registered brand and a registered campaign that describe who you are and what you send. Gateway traffic has neither. Carriers rate-limit gateways to stop spammers from using them as free bulk channels. They apply aggressive filtering to anything that looks automated, and they quietly drop messages that trip a filter. Our post on 10DLC enforcement explains what happens to unregistered business traffic on regular numbers. Gateways have the same problem with less visibility.

No delivery receipts, no error codes

When an email to a gateway fails, you usually hear nothing. The mail server accepts the email, and whatever happens on the carrier side never comes back to you. You can't tell "delivered" from "filtered" from "number ported away." An appointment reminder that silently fails costs you a missed appointment and gives you no record of why.

Replies are unreliable

When someone replies to a gateway text, the reply may come back as an email, may come from a different address than the one you sent from, or may not come back at all. Threading breaks, and nobody on your team sees a clean conversation.

Formatting gets mangled

Gateways prepend the sender address or subject line, cut long bodies at around 160 characters, and handle links and attachments inconsistently. Your 140-character message plus a 40-character sender prefix becomes a cut-off text.

Compliance is entirely on you

A gateway won't process a STOP reply, hold messages during quiet hours, or record that you had permission to text. If a recipient texts STOP and you keep sending, that's your problem, and TCPA exposure runs roughly $500 to $1,500 per text.

When a gateway is genuinely fine

Here's where the gateway still works:

• Alerts to your own phone. A cron job emailing you when a disk fills up is fine. You know your carrier, you consented, and a missed alert is annoying rather than costly.
• Internal pings to a few staff phones. You can work with this if you confirm each person's carrier and accept that some messages will go missing.
• Testing and prototyping, before you commit to a provider.

The gateway stops being a good choice once you text customers, need proof of delivery, expect replies, or send more than a handful a day. If what you need is the email workflow itself, where staff type into an inbox and a text goes out, our guide to email to text for business covers how to keep that habit on a registered route.

The registered alternative: send through an SMS API

The replacement is an HTTP call to a messaging API that sends from a registered number. You give it the phone number in E.164 format and it figures out the carrier. It returns a result you can log, sends replies back into an inbox or your system, and handles opt-outs.

We make Ready, so here's what that looks like on our API:

curl -X POST https://api.tryready.com/v1/messages \
  -H "X-API-Key: $READY_API_KEY" \
  -H "Idempotency-Key: 7b1e4c2a-9f3d-4a61-8c0e-2d5f6a7b8c90" \
  -H "Content-Type: application/json" \
  -d '{"to": "+12125550199", "body": "Your order #1042 has shipped.", "consent_attested": true}'

A few points the gateway can't match:

• No carrier lookup needed. You send to the number, not to a carrier's domain.
• The Idempotency-Key means a retried request never sends the same text twice.
• consent_attested is your statement that the recipient agreed to texts. Ready records that attestation per send (who sent, to how many, when). It is not a per-contact consent record. Your store or signup form still needs to keep when and how each person opted in.
• Opt-outs are refused up front and not charged. A STOP reply is honored automatically and applies across every campaign.
• Quiet hours are enforced. A text sent outside the recipient's permitted local hours is held only if the window opens within 6 hours; otherwise it is refused with 409 QUIET_HOURS_BLOCK and you send it again. A held text is charged only when it goes out.

For bulk sends, POST /v1/messages/bulk takes up to 100 recipients per call. Full request details are in the messages docs and the quickstart. For the broader picture of app-to-person texting from your own software, see our post on the A2P SMS API.

What it costs: a worked example

A gateway is free per message. A registered API isn't, so here's an honest look at the cost.

Assumptions: a service business sends 300 appointment reminders a month. Each is about 140 plain characters with no emoji, so each is 1 segment. Roughly 60 people reply.

• Outbound: 300 segments × $0.0075 = $2.25, plus 300 × $0.0045 carrier fee
• Inbound replies (billed like sent texts): 60 × $0.0075 = $0.45, plus 60 × $0.0045
• Registration: $25/mo for registration and $2/mo per number

That's the two sums above plus $27 a month fixed with one number, and the carrier fees on top. The carrier fee is itemized separately on the bill. These figures are all-in except for the compliance surcharge: TCPA/DNC scrubbing and landline validation are each $0.003 extra per segment when switched on, and both are off by default.

Raw CPaaS APIs such as Twilio (about $0.0083 a segment) charge less per segment. What Ready adds is registration handled in-app, the inbox, opt-out and quiet-hours handling, and campaigns in one place. Pick the option that matches how much you want to build yourself.

Moving off a gateway: a short checklist

1. List every place that emails a gateway address. Look in cron jobs, form handlers, help desk rules and printer or alarm panels.
2. Confirm consent for every customer number you text, and keep the record in your own system.
3. Sign up and get a number. The first 20 texts are free one-to-one sends, so use them for testing before you register. They end as soon as a registration is paid for. To send, you add a card and get a number, which is $2 a month with the first month charged when you get it.
4. Register your brand and campaign. The first month, $25, is charged at submit. Most approvals take 2 to 7 days. An account can send up to 500 texts a month before registering.
5. Swap the email call for the API call and log the response.

The practical takeaway

Emailing a phone number is fine for alerts to yourself. For anything a customer receives, it's an unregistered, unmonitored route that carriers are filtering harder or shutting down. A registered API costs a few dollars a month at small volume and tells you whether each message actually arrived. If you want to try it, create an account, send your 20 free texts to your own phones, and see how the replies thread before you move anything else over.