I’m currently experiencing issues allowing IPv6 traffic in my AWS security group, specifically when trying to connect to an SMTP server over IPv6 from my EC2 instance. Here’s the setup:

I have an EC2 instance running a Django application.
The application needs to send emails using an SMTP server (smtp.gmail.com).
The SMTP server supports both IPv4 and IPv6 connectivity.
I have correctly configured the Django application to send emails via SMTP.
However, when the application attempts to establish a connection to the SMTP server over IPv6, I’m encountering connection timeout errors. Here’s what I’ve tried so far:

Checked IPv6 connectivity: Verified that my EC2 instance has IPv6 enabled and is correctly configured to support IPv6 connectivity.
Updated security group rules: Added inbound and outbound rules to the security group associated with the EC2 instance to allow traffic on port 587 for both IPv4 and IPv6.

Tested IPv6 connectivity: Used tools like ping6 and telnet to verify connectivity to the SMTP server’s IPv6 address (2a00:1450:400f:80d::2004 for smtp.gmail.com).
Despite these efforts, I’m still experiencing connection timeout errors when trying to connect to the SMTP server over IPv6 but connected to IPv4 after some time
Outbound rule.
Inbound rule

Could someone please provide guidance on how to troubleshoot and resolve this issue? Are there any additional configurations or steps I might be missing to enable IPv6 connectivity in my AWS environment?

Thanks in advance for any help or insights you can provide.

What I Tried:

Verified IPv6 Configuration:
Checked that my EC2 instance has IPv6 enabled and correctly configured.
Confirmed that the instance has an IPv6 address assigned.
Ensured that the VPC and subnet configurations support IPv6.

Updated Security Group Rules:
Added inbound rules to allow traffic on port 587 (SMTP) for both IPv4 and IPv6.
Added outbound rules to allow traffic on port 587 for both IPv4 and IPv6.
Specifically, added rules allowing all ICMPv6 traffic to diagnose potential network issues.

Tested Connectivity:
Used telnet to attempt a connection to the SMTP server over IPv6 (telnet smtp.gmail.com 587).
Used ping6 to test connectivity to various IPv6 addresses, including Google’s IPv6 address (ping6 ipv6.google.com).
Used dig to ensure proper DNS resolution for AAAA records (dig AAAA www.google.com).
Checked Firewall and Routing:

Verified that there are no local firewalls on the EC2 instance blocking IPv6 traffic.
Ensured that the VPC route tables are correctly configured to route IPv6 traffic.

What I Was Expecting:

I expected that the connection to the SMTP server over IPv6 would be established without timeouts, similar to how it works over IPv4.
I anticipated that with the correct security group and network configurations, the EC2 instance would successfully connect to the SMTP server’s