Troubleshooting SMS Delivery Failures: A Comprehensive Guide

Overview

SMS delivery can fail at different stages — from the PXME platform, through carriers, or at the recipient’s phone. Failures are often tied to account restrictions, invalid numbers, carrier limitations, or opt-outs. This guide explains how SMS delivery works, how to locate errors, and how to resolve the most common issues across PXME, carrier, and phone layers.

1. Understanding SMS Delivery

Q: How does SMS delivery work?
A:
When you send an SMS, it passes through these stages:

1. PXME platform processing

2. Phone number validation

3. Carrier network delivery

If a failure occurs at any stage, the SMS won’t be delivered.

2. Locating Sending/Delivery Errors

Q: How can I find the error if my SMS fails to send or deliver?
A:

• Errors appear inside the Conversation View of your PXME account.

• Each failure comes with an error code that indicates the reason.

• Use the error code as a reference for troubleshooting.

3. Common Causes of Delivery Failures

Issues at the PXME Level

Q: What happens if Do Not Disturb (DND) is enabled for a contact?
A: PXME blocks the SMS from sending and shows an error.

Q: What if the phone number is a landline or not SMS-capable?
A: PXME validates numbers before sending. If invalid, delivery fails.

Q: Why can’t I send messages from a new account?
A: New accounts have gradual sending limits to prevent misuse. Limits increase over time or can be manually adjusted.

Q: Why am I getting an error about exceeding my daily SMS limit?
A: Each account has a daily SMS quota. Bulk SMS pauses when exceeded, but 1:1 direct messages still deliver.

Q: Why has my account’s SMS sending been suspended?
A: Accounts may be suspended due to:

• High error rates

• High opt-out rates

• Carrier complaints

All SMS attempts will fail until reviewed by support.

Issues at the Phone Layer

Q: What happens if the recipient’s number is on the DND list?
A: Messages cannot be delivered. The contact must opt back in by texting “START.”

Q: What does a “Queue Overflow” error mean?
A: Too many messages queued at once. PXME holds them for up to 4 hours before marking as failed. Stagger sends or lower validity periods.

Q: What if my account is suspended after queuing a message?
A: SMS will fail if suspension occurs before sending. Contact support to review.

Carrier Network Issues

Q: What does “Unreachable Destination Handset” mean?
A: The recipient’s phone is:

• Switched off

• Out of service

• Not SMS-capable (e.g., landline)

Q: Why is my message being blocked?
A: Carriers may block if:

• The handset can’t receive SMS

• The recipient is on a Do Not Call registry

• The recipient opted out with STOP

• You’re sending from a toll-free number to an opted-out contact

Q: Why did my message fail due to attachment size?
A: Attachments must be under carrier limits. Large files cause failures.

Q: Why are international SMS messages failing?
A: Some countries block external SMS or restrict content. Verify delivery support for the country.

Q: My message exceeds 1600 characters. Why won’t it send?
A: SMS has a 1600-character limit. Exceeding this prevents delivery. Watch for dynamic content (custom values) that can cause overflow.

Costs

Q: Why am I being charged for SMS messages that failed to deliver?
A: Charges apply once delivery is attempted, even if the carrier or handset rejects it. This covers network costs for attempted delivery.