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Self-hosting email in 2026, with local LLM spam filtering

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Spend a week in self-hosting circles and someone will say it: self-host anything except email.

Blocklists, spam folders, delivery nightmares — the stories are real. In 2026, though, the last big blocker is mostly solved: local LLMs + rspamd can classify spam on par with big providers, without sending your mail to a cloud API.

This walkthrough follows Christian Haschek, an MSP who migrates companies off Gmail and Microsoft — and moved his own Google Workspace to self-hosted mail.

Self-hosted mail and data sovereignty

Can you run it at home?

A VPS is the safe default. Home works if all of this is true:

RequirementWhy
Static IPv4Dynamic IPs break MX/PTR; check blocklists first
No CGNATCarrier-grade NAT blocks inbound port 25
Editable PTRReverse DNS must resolve to mail.yourdomain.com — ISP ticket required
Open ports25 143 465 587 993

Will a short outage lose mail? Usually no. SMTP senders retry. The author’s rule of thumb: <40% daily downtime still delivers fine.

Which mail stack?

OptionBest for
docker-mailserverDefault pick — Docker, sane defaults
StalwartModern Rust stack
MailcowAll-in-one with web UI
Hand-rolled Postfix+DovecotLearning / masochism

He runs legacy ISPConfig; greenfield today → docker-mailserver.

DNS: miss one record, miss the inbox

SPF

v=spf1 mx a ~all

DKIM

Server generates keys; publish the public TXT:

v=DKIM1; t=s; h=sha256; p=MIGf[...]B;

DMARC

Policy layer on SPF/DKIM — use a DMARC generator if unsure.

MX + A

  1. mail.yourdomain.com → A record → server IP
  2. MX priority 10 → mail.yourdomain.com

PTR

Only your ISP or VPS provider can set this. The IP must reverse to mail.yourdomain.com or major providers bounce you.

DNS records and deliverability

Before go-live: send a test message through mail-tester.com — SPF, DKIM, DMARC, blocklists, content score in one place.

Antispam: local LLM changed the game

Classic OSS antispam (IP lists, keywords, Spamhaus) was bad enough to drive people back to Gmail. Big tech wins on volume — billions of messages per day.

Stack: rspamd GPT plugin + local llama.cpp

rspamd already does DNS, Bayes, blacklists. The GPT plugin sends headers + subject + body to an LLM and expects JSON:

{
  "probability": 0.85,
  "reason": "unsolicited commercial content with suspicious Punycode URL"
}

Privacy rule: never ship full mail to OpenAI. Run the model locally.

Model and install

Model: unsloth/gemma-4-12B-it-qat-GGUF:UD-Q4_K_XL — ~7GB RAM/VRAM, multilingual.

curl -LsSf https://llama.app/install.sh | sh

llama serve -hf unsloth/gemma-4-12B-it-qat-GGUF:UD-Q4_K_XL \
  --reasoning off -fa on -c 16000 --temp 0.7

Hit http://localhost:8080 — if the chat UI loads, the API is ready.

rspamd config

/etc/rspamd/local.d/gpt.conf:

allow_ham = true;
allow_passthrough = true;
enabled = true;

type = "openai";
url = "http://192.168.1.5/v1";
model = "unsloth/gemma-4-12B-it-qat-GGUF:UD-Q4_K_XL";
api_key = "this-is-ignored-on-llama.cpp";

max_tokens = 100;
temperature = 0.1;
timeout = 30.0;
json = true;

prompt = "You are an expert email spam classifier. Analyze the following email headers, subject, and body. Respond with a JSON object containing two keys: 'probability' (a floating point number between 0.0 and 1.0 indicating spam probability) and 'reason' (a short sentence explaining why). Output only the raw JSON object, no markdown code fences.";

context {
  enabled = true;
  level = "user";
  min_messages = 5;
  message_ttl = 1209600;
  ttl = 2592000;
}

The context block stores per-recipient digests in Redis (14-day window) and injects them after 5+ messages — classification adapts to your inbox, still 100% local.

Local LLM mail classification pipeline

No GPU? Raise timeout; CPU inference is slower but works.

Use rspamd’s web UI to paste messages and see how they would score — essential for tuning prompts and thresholds.

Clients

Desktop: Thunderbird — open source, solid search, Android app. Prefer webmail? Mailcow and similar bundles include a panel.

Ops: control means responsibility

Modern stacks auto-apply security updates, but backups and restore drills are on you:

  • Lost mail data = lost business and personal history
  • Run at least one “pretend the disk died” recovery
  • Remote access, key rotation, rspamd updates — put them on a checklist

Mail server ops and backups

Quick decision table

SituationRecommendation
Static IP + PTR, privacy-firstHome docker-mailserver + local LLM
Shaky home networkVPS + same stack
Just want @mydomain.com, no MTACloudflare Workers path (e.g. Cloud-Mail)
Team + complianceMailcow or managed host + strict backups

Bottom line

It works. Brief downtime rarely loses mail; DNS/PTR and spam — the hard parts — now have mature answers.

If you already run a homelab and a local LLM, wiring rspamd is probably the highest-leverage next step: Gmail-class filtering, data never leaves your network.

Source: You should self-host your mail server

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