add postfix deployment and service

[maneeshaxyz]

📌 Description

• Closes [TASK] Get Postfix working in the Infra setup. #250

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🔍 Changes Made

• Made initial file structure using file structure doc.
• Added postfix deployment file.
• Added postfix service yaml file.

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✅ Checklist (Email System)

• Core services tested (SMTP, IMAP, mail storage, end-to-end delivery)
• Security & compliance verified (auth via Thunder IDP, TLS, DKIM/SPF/DMARC, spam/virus filtering)
• Configuration & deployment checked (configs generated, Docker/Compose updated)
• Reliability confirmed (error handling, logging, monitoring)
• Documentation & usage notes updated (README, deployment, API)

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[gemini-code-assist]

Summary of Changes

Hello @maneeshaxyz, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces the necessary Kubernetes deployment configuration to provision a Postfix SMTP server. This deployment is a foundational step towards establishing a robust email system, integrating key configuration files and data volumes to ensure proper operation and persistence within the Kubernetes environment.

Highlights

• New Kubernetes Deployment: Introduces a new Kubernetes Deployment manifest (postfix-deployment.yaml) to deploy an SMTP server using the silver-smtp Docker image.
• Postfix Configuration: Configures the Postfix server with environment variables for hostname and network, and mounts various configuration files (e.g., main.cf, master.cf, virtual domain/user/alias maps) from host paths.
• Volume Mounting: Utilizes hostPath volumes to persist Postfix configuration, Let's Encrypt certificates, and Raven data, ensuring the server uses external configurations and data.

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[gemini-code-assist]

Code Review

This pull request introduces a Kubernetes deployment for Postfix. While this is a good step, the current configuration has several critical security and operational issues that need to be addressed. My review includes feedback on using hostPath volumes, running the container as root, configuring an open relay, and other best practices for Kubernetes deployments such as using immutable image tags, setting resource limits, and configuring health probes.

[gemini-code-assist]

Setting MYNETWORKS to 0.0.0.0/0 configures Postfix as an open relay, which is a critical security vulnerability. This allows anyone on the internet to send email through your server, which will be quickly abused for sending spam and can result in your server's IP address being blacklisted. This value should be restricted to trusted networks only, such as your internal Kubernetes pod and service CIDRs.

            - name: MYNETWORKS
              value: "127.0.0.0/8"