AWS SNS is not sending SMS anymore

Question

I have been using Amazon SNS to send SMS for a while, but two days ago it stopped working. I didn't change anything on my side. Even if I try to send SMS from the console, it still doesn't work.

I only have 35% delivery rate for last couple of days, but since yesterday it is not working at all.

Answer 1

There are different ways to troubleshoot this problem. This is something addressed in the Developer Forum of AWS. Please go through the following steps to troubleshoot this problem. These could be basic steps, but I am pointing out the most general steps required.

1. Try sending an SMS from the AWS Console. If this works, there is no issue with the spending limit or delivery rate. (So you have mentioned that this is not working too)
2. Now check whether your Mobile number (which is receiving SMS) is subscribed to the topic. Under some conditions, the recipient can opt out from the topic.

Where required by local laws and regulations (such as the US and Canada), SMS recipients can opt out, which means that they choose to stop receiving SMS messages from your AWS account.

3. Check the Account Spending Limit which you have set for your calendar month. This could be limiting your SMS delivery. If you haven't set this, the default is 1 USD per month.

For Account spend limit, type the maximum amount in USD that you want to spend on SMS messages each calendar month. When Amazon SNS determines that sending an SMS message would incur a cost that exceeds your spend limit for that month, Amazon SNS stops publishing SMS messages within minutes.

4. For much more obvious reasons, check whether your Mobile Number (Which is receiving SMSs), is not blocking any of your SMSs.
5. If none of these work, do contact AWS support team, they will get back to you within 2 working days. They will definitely sort it out. Until now, all my support calls were successfully resolved by their team.

Answer 2

Since yesterday, the messages have completely stopped coming so you might have reached the SNS SMS spend limit for your account. By default it is 1 USD for a AWS account in a AWS region. You should get your limit increased.

But in future if you want to prevent this i.e. if you want to get notified earlier before you reach the actual SMS Spend Limit for your account so that limit can be increased before hand. In this way you would not face SMS delivery issues due to limit being reached. You can create a CloudWatch Alarm on your SMSMonthToDateSpentUSD metric.

Please have a look at this video: https://www.youtube.com/watch?v=5-HdLf_lizI