The SNS service in sns.ap-southeast-2 is not working when invoked from the EC2 instance.

I’m trying to send emails via the AWS SNS service, via a script on the EC2 instance however I’m getting a time out error message.

To validate this tried running curl and got the following curl -v https://sns.ap-southeast-2.amazonaws.com

• Host sns.ap-southeast-2.amazonaws.com:443 was resolved.
• IPv6: (none)
• IPv4: 172.31.28.33, 172.31.38.196, 172.31.15.41
• Trying 172.31.28.33:443...
• connect to 172.31.28.33 port 443 from 0.0.0.0 port 63081 failed: Timed out
• Trying 172.31.38.196:443...
• connect to 172.31.38.196 port 443 from 0.0.0.0 port 63083 failed: Timed out

I have re-validated the security configurations of the EC2 instance, and all the settings required to publish the SNS message are configured properly:

1. Validated the IAM role associated with the EC2 instance.
2. Checked the subnet configuration.
3. Reviewed ACL (Access Control List) settings.
4. Inspected inbound and outbound rules.

However, I noticed that the issue occurs specifically with the SNS topic in the **ap-southeast-2 region. **I tried using another region, and it worked as expected.

Additionally, I ran an nslookup, and the results for ap-southeast-2 are unusual compared to those of other regions (please find the attached results).

Please find the screen-shot of Curl Response from other region

Note: SNS of the problematic region (ap-southeast-2) worked from Lambda function as well as from my personal laptop using the script.

Therefore, I kindly request you to share the resolution steps to overcome this issue.