Features · everything in arc-relay

What's
under the hood.

The relay that keeps the sender’s authentication on the record. ARC sealing and SRS rewriting on forwarded mail, delegated DKIM signing on Pro and above. Plus optional grounded AI replies, block rules, webhooks, and a full API/MCP surface.

On this page

01 Forwarding 02 Email auth (DMARC) 03 Block rules 04 Optional AI replies 05 API & webhooks

01Forwarding

Every alias on your domain, one inbox.

Catch-all by default. Per-alias by choice. Nothing gets lost — even mail to addresses you've never made.

FIG.01 — RELAY TOPOLOGY

TLS · DKIM · DMARC · SPF

04Optional AI replies

Auto-replies that actually know your product.

Each domain gets its own knowledge base — markdown files, FAQs, policies — and a persona you define. The assistant retrieves what's relevant and replies. Credit-capped, so a runaway thread can't run up the bill.

Jordan Mehta

[email protected]

09:14

Quick question — does the free plan include DKIM signing, or do I need to upgrade?

◇ AUTO-REPLY · KB-GROUNDED

Hi Jordan,

DKIM signing kicks in on the Pro plan and above — outbound forwards get signed automatically. The free tier still gets ARC sealing + SRS rewriting, just no DKIM signature on the relay.

Best,

◇ SENT · sourced from KB arc-relay-support · 1 credit

2.1

Knowledge base

Drop markdown into the domain's KB folder — vector-indexed and retrieved per query

2.2

Persona per domain

A custom system prompt sets voice, rules, and what the assistant won't say

2.3

Auto-appended footer

Your support address and signature attached to every reply

2.4

Prompt-injection guard

Ignores instructions hidden in inbound mail trying to override the persona

2.5

Credit cap

Hard monthly limit per plan. Bot stops drafting when you hit it — costs never surprise you.

03Block rules

Catch-all by default, blocks where you draw the line.

Catch-all forwarding picks up mail to any address on your domain — even ones you've never made. Per-alias overrides redirect specific addresses elsewhere. Sender block rules drop unwanted senders by email or domain pattern before they reach you.

◇ curl · block a sender

BASH

curl -X POST https://api.arc-relay.com/v1/sender-rules \
  -H "Authorization: Bearer $ARC_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "sender_pattern": "@spammer.example",
    "action": "block"
  }'

02Email auth (DMARC)

Authentication that survives the relay.

Plain forwarding breaks SPF, and DMARC with it unless the message carries an aligned DKIM signature. We seal the message with ARC, recording the SPF, DKIM and DMARC results checked when it arrived, rewrite the envelope with SRS, and sign outbound with DKIM (Pro+), so the receiving server has those results to weigh.

◇ SPF

Envelope sender rewritten with SRS, so SPF is checked against ARC-Relay's domain

◇ DKIM

Outbound forwards signed with your relay key (Pro+)

◇ DMARC

The DMARC result checked on arrival is recorded in the ARC seal

◇ ARC

Authenticated Received Chain seals the auth result at each hop

◇ SRS

Sender Rewriting Scheme keeps the bounce path valid

◇ TLS

Encrypted transport to your destination mail server

05API & webhooks

Every UI action is a REST call.

If you can do it in the dashboard, you can script it. Webhooks fire on receive, forward, reply-drafted, reply-sent, and bounce events.

◇ curl · create alias