goemail

goemail

Summary

goemail is an AWS Lambda function written in Go that handles SES inbound emails. It forwards emails arriving at any address on your domain to a designated target email address (e.g., your Gmail). It includes features for tracking original recipients and blocking unwanted senders/recipients via an S3-backed blocklist.

Features

• Email Forwarding: Automatically forwards inbound SES emails to a configured EMAIL_TO address.
• Original Address Reflection: Adds X-Original-To and X-Original-From headers to forwarded emails. This allows you to see the original recipient in your inbox, which is useful for identifying which alias received the email.
• S3-Based Blocklist: Prevents forwarding of emails sent to addresses listed in a blocks.txt file stored in S3.
• Remote Blocklist Management: Add addresses to the blocklist by sending an email:
  • From: Your configured EMAIL_TO address.
  • Subject: block (case-insensitive).
  • To: The address(es) you wish to block.
  • Result: The system updates the blocklist and sends a confirmation email.
• Robust Header Handling: Correctly handles multi-line (folded) headers and performs normalization of email addresses for reliable matching.
• Error Handling: Provides detailed logging and sends administrative alerts if forwarding fails, including pre-signed S3 links for manual retrieval.

Build

The project uses Mage for build and deployment automation.

• Build: go build .
• Test: go test ./...
• Deploy: mage deploy (requires AWS credentials and a .env file).

Setup

1. Environment Configuration: Create a .env file in the root directory with the following variables:
   • EMAIL_BUCKET: The S3 bucket where SES stores inbound emails.
   • EMAIL_FROM: The address that will appear in the From header of forwarded emails (must be a verified identity in SES).
   • EMAIL_TO: Your target destination email address.
   • GO_LAMBDA_NAME: (Optional) The name for the Lambda function.
2. AWS Infrastructure:
   • The mage deploy command handles the creation/update of the Lambda function and its IAM role.
   • The IAM role is automatically granted AmazonS3FullAccess, AmazonSESFullAccess, and AWSLambdaBasicExecutionRole permissions.
   • You will need to configure SES Receipt Rules to store incoming emails in the S3 bucket and trigger this Lambda function.
3. SES Configuration:
   • Identities: Verify your domain and the EMAIL_TO recipient address in the SES "Identities" section.
   • MX Records: Configure your domain's DNS with MX records pointing to the AWS SES receiving endpoint (e.g., 10 inbound-smtp.us-east-1.amazonaws.com).
   • Receipt Rule Set: Create a default rule set with a rule that includes:
     1. S3 Action: Delivers the raw email to the bucket specified in EMAIL_BUCKET.
     2. Lambda Action: Invokes the goemail Lambda function using the "RequestResponse" invocation type.
   • Permissions: Ensure that the S3 bucket policy allows SES to write to it and the Lambda function has a resource-based policy allowing ses.amazonaws.com to invoke it (handled automatically by mage deploy).

created by tigwen