SMTP Relay Server VPS Hosting on Anubiz Host

Most application stacks start by sending mail directly through a transactional API like SendGrid, Mailgun, or Postmark. That works until pricing scales nonlinearly, until your account gets suddenly suspended for sending content the provider does not like, or until you simply do not want a third party reading every outbound message your application generates. Running your own SMTP relay on an Anubiz Host offshore VPS solves all three problems. Your application talks to a private Postfix or Haraka relay over an internal IP or TLS-protected port 587 submission. The relay then handles MX lookup, TLS negotiation, retry logic, bounce handling, and DKIM signing on the outbound side. This pattern is especially common for SaaS founders who do not want SendGrid throttling their notification volume, e-commerce operators whose payment confirmations cannot afford a third-party outage, and crypto projects who simply cannot get a clean account on a US-based ESP.

A minimal Postfix relay configuration on Anubiz Host VPS is straightforward. Install Postfix from the distribution package, set inet_interfaces to listen only on a private VPN or trusted IP for submission, and configure smtpd_relay_restrictions to permit only authenticated submissions and trusted internal networks. Outbound TLS via smtp_tls_security_level set to encrypt is mandatory. Add OpenDKIM with a signing key per sending domain, publish the public key in DNS, and align the SPF record to include your relay IP. DMARC starts in quarantine mode while you tune deliverability, then promotes to reject once you have measured a clean alignment for 30 days. For higher volumes, point Postfix at Rspamd as a milter to score and quarantine any abusive mail your own applications might accidentally generate. Rspamd also makes it easy to enforce per-user or per-application sending rate limits.

A single Anubiz Host offshore VPS comfortably relays tens of thousands of messages per hour with a modest 4 vCPU and 4GB RAM configuration. The bottleneck under sustained load is usually the receiving MX server, not the relay itself. For sustained throughput above 100k messages per hour, scale horizontally by deploying multiple relay nodes behind a round-robin DNS or HAProxy and use a shared Redis instance for sender reputation state. When standing up a fresh SMTP relay, IP warm-up matters. Start with a few hundred messages per day to each major destination, increase by 50 percent daily, and watch deferred and bounce counts in Postfix logs. Within two weeks of warm-up, your relay reputation is solid. Bounce handling should always land in a dedicated VERP mailbox that your application can read programmatically. Postfix has native support for VERP envelope addressing, and parsing bounces lets you suppress unreachable recipients automatically.