Key Takeaways
- Scheduled SMS is a queue plus a radio. A green calendar in your app is not a send if the handset slept.
- Store the wall clock and IANA zone you meant. “Tomorrow 9am” without a zone is a geo outage.
- After power cuts, pace the backlog. A dump of overnight jobs empties airtime and looks like a blast.
- Keep OTP off scheduled promo devices. Consent and STOP still apply to campaigns.
- You bring the Android and operator credit. Platform pricing is devices plus send volume — schedules do not include airtime.
android sms gateway scheduled sms fails in the gap between “we queued it” and “the SIM transmitted.” Pillar: scheduled SMS campaigns. This in-depth guide is timezone, OEM sleep, and backlog pace — not a rewrite of that page.
You supply the phone and airtime. Devices and send volume. Timezone scheduling. Live JSON: Developer Center.
Due time · radio time
The clock can be right while the phone is in Doze.
Whose clock fires
Decide whether due time is server UTC, the phone’s wall clock, or the recipient’s zone — then write it down. Mixed fleets across WIB/WITA or US coasts will send “9am” six hours wrong. Gateway overview. REST samples are HTTPS/JSON, not a scheduling SDK product.
A campaign that fires from a sleeping phone is not late. It is unsent. Your analytics will still call it scheduled.
Failure matrix
| Symptom | Likely cause | Check | Fix |
|---|---|---|---|
| Nothing at due time | OEM kill / battery | Pairing + exemptions | OEM restrictions |
| Sent at 3am local | Wrong zone | IANA zone on the job | Timezone how-to |
| Burst after outage | Backlog dump | Queue depth | Pace the catch-up |
| Accepted, empty prepaid | Airtime | Operator wallet | Top-up before the window |
Timezones and quiet hours
Quiet hours and consent are counsel + your list, not a feature toggle that erases TCPA/local rules. Consented bulk, STOP. Messaging practices. DLR still means carrier-reported, not “they read it at 9:01.” Delivery reports.
The phone must be awake
Charged, paired, OEM-exempt, funded. App uptime. Spare device if the window matters. Multi-device. Canary a one-off schedule to a staff MSISDN on a cold phone. Real handsets.
Do not schedule OTP
Codes have TTLs. A scheduler plus a sleeping radio is how logins fail at 08:59. OTP stays on-demand on a quiet pool. Isolate promo schedules from that pool. CSV.
Next steps
Document zone + quiet hours, OEM-exempt the sending phone, schedule one canary. Install the app. Spend 300 lifetime SMS proving the window before a customer list.
Related product pages
Jump to the live product docs for this topic—not another long-form article.
- scheduled SMS campaignsSend later windows
- device and SMS volume pricingPlans and allowances
- Android SMS gateway product guideDefinition, product, and how to buy
- SMS API documentationLive endpoint reference
