Technical Lab Journal

Date: July 21, 2026

Project: Mailcow Docker Stack Deployment & Mail Deliverability Hardening

Target Domain: scottdiemer.com | IP: 107.173.164.131

1. Core Infrastructure & Deployment

Deployed containerized Mailcow mail server stack (Postfix, Dovecot, Rspamd) via Docker Compose on an Ubuntu VPS host.

Configured primary service endpoints for inbound and outbound mail handling.
Connected the mail infrastructure to an internal osTicket deployment by mapping database backends to resolve API authentication failures and enable automated helpdesk operations.

Mailcow Admin Dashboard UI

Established end-to-end cryptographic and identity verification protocols across DNS:

PTR (Reverse DNS): Configured IPv4 PTR record mapping 107.173.164.131 directly to mail.scottdiemer.com to pass reverse lookup verification.
DKIM: Generated and published public DKIM keys via DNS TXT records to digitally sign outgoing messages and prevent header tampering.
DMARC: Authored policy TXT records to specify enforcement actions and establish domain alignment rules.
SPF Syntax Correction: Resolved an initial syntax failure caused by literal square brackets around the IP address (ip4:[107.173.164.131]). Corrected the record to standard SPF format (v=spf1 ip4:107.173.164.131 ~all), establishing full identity authorization for outbound mail.

DNS TXT Records with DKIM and SPF

Configured Postfix explicitly to prefer IPv4 outbound routing (smtp_address_preference = ipv4 and inet_protocols = ipv4) to avoid container networking conflicts with unrouted IPv6 subnets.
Performed deliverability and spam heuristic checks through Mail-Tester, successfully validating complete protocol alignment and achieving a 10/10 score.

Mail-Tester 10 out of 10 Score Result

Provisioned standard service mailboxes (support@scottdiemer.com and scott@scottdiemer.com).
Successfully integrated mail accounts across desktop (Thunderbird) and mobile (Gmail App via IMAP/SMTP) clients using TLS encryption.