How to get incoming mail in IPv6

To enable incoming mail over IPv6 for your SmarterMail server on Amazon EC2, you'll need to configure several AWS components:

1. First, ensure your VPC has IPv6 support. You'll need to associate an IPv6 CIDR block with your VPC and the subnet where your EC2 instance is running.

2. Update your EC2 instance's security group to allow incoming mail traffic over IPv6. In the Amazon VPC console, select your security group, go to "Inbound rules," and add rules that allow SMTP traffic (typically port 25) from IPv6 addresses by specifying ::/0 as the source.

3. Assign IPv6 addresses to your EC2 instance. All current generation instance types support IPv6, but some older types (C1, M1, M2, M3, and T1) do not.

4. For Amazon SES email receiving, you'll need to set up IP address filters to control incoming mail. By default, all mail originating from Amazon EC2 IP addresses is blocked, so you'll need to add your IPv6 addresses to your allow list.

5. Create IP address filters in the Amazon SES console by navigating to "Email Receiving" > "IP Address Filters" and creating filters that allow mail from the IPv6 addresses you want to receive mail from.

Remember that if you want to receive mail only from specific IPv6 addresses, you should set up a block list with a broad range and then create specific allow entries for trusted IP addresses.
Sources
Add IPv6 support for your VPC - Amazon Virtual Private Cloud
Amazon SES email receiving concepts - Amazon Simple Email Service
Manage the IPv6 addresses for your EC2 instances - Amazon Elastic Compute Cloud
Creating IP address filters for Amazon SES email receiving - Amazon Simple Email Service

Hi Lennart,

You're correct — enabling IPv6 for incoming mail on Amazon EC2 does require a few more setup steps beyond just enabling the protocol on your mail server. Here's how to make sure everything is configured correctly on the AWS side:

1. Ensure Your VPC Supports IPv6 Go to your VPC settings in the AWS Console.

Make sure the VPC and the subnet your EC2 instance uses both have an associated IPv6 CIDR block.

If not, assign one by editing the subnet and enabling auto-assignment of IPv6 addresses.

2. Assign an IPv6 Address to Your EC2 Instance Navigate to your EC2 instance.

Under Network Interfaces, choose the interface (ENI).

Click Manage IP addresses → assign a new IPv6 address.

You may also want to set up a static (EIPv6) if needed for DNS/MX records.

3. Update Security Group Rules for IPv6 Mail Go to your EC2 security group.

Under Inbound rules, add a new rule:

Type: SMTP (or Custom TCP)

Port: 25 (or 587/465 if you're using submission)

Source: ::/0 (or a restricted IPv6 block if applicable)

This allows incoming email traffic via IPv6.

4. Update Your DNS Records (MX and AAAA) Ensure your domain has a valid MX record pointing to your IPv6-enabled hostname.

That hostname should resolve via an AAAA record to the IPv6 address of your EC2 instance.

5. Verify SmarterMail Listens on IPv6 Double-check your SmarterMail config (usually under Bindings or Protocol Settings).

Ensure it's listening on both IPv4 and IPv6 interfaces for SMTP.

Notes You do not need Amazon SES unless you're using it to receive email (which is not the case here).

Make sure your mail server is not blocking the IPv6 interface internally (some firewalls or OS settings might be limiting this).

Let me know if you’d like help testing external delivery to your IPv6 setup — happy to help!

— (Shared to support others configuring IPv6 email on EC2 with custom mail servers.)