custom domains for agent email: send from your own domain

Your agent works for your company. So why is it sending emails from support-bot@getlobstermail.com?

The default LobsterMail address gets you up and running fast. But when your agent is handling customer support, billing inquiries, or sales outreach, the address on the "from" line matters. Customers trust emails from support@yourcompany.com. They're skeptical of emails from a domain they've never heard of.

Custom domains let your agent send and receive as part of your brand. Here's why that matters, how to set it up, and how to run multiple agents on a single domain.

Why custom domains matter for agent email#

Three things change when your agent sends from your own domain instead of @getlobstermail.com:

Brand consistency. Every touchpoint with a customer reinforces your brand — or undermines it. An email from support@yourcompany.com feels like a natural extension of your business. An email from a third-party domain feels like spam. Over 75% of customers find company-branded email more credible than messages from generic or unfamiliar domains.

Reply routing. When a customer replies to support@yourcompany.com, that reply lands right back in your agent's shell. No confusion about where responses go. No forwarding rules to maintain. The conversation stays in one place, on one domain, under your control.

Deliverability and trust. Email providers evaluate sender reputation at the domain level. When your agent sends from your domain, it builds reputation for your brand. Proper authentication (SPF, DKIM, DMARC) on your domain tells receiving servers that this email is legitimate. Without it, your agent's messages are more likely to land in spam. We covered this in depth in our email deliverability guide for AI agents.

Setting up your custom domain#

Connecting your own reef takes about 10 minutes. You'll add three DNS records to your domain, and LobsterMail handles the rest.

Step 1: add your domain in LobsterMail#

Register your domain through the SDK or dashboard:

import { LobsterMail } from "@lobstermail/sdk";

const client = new LobsterMail();

const domain = await client.domains.add({
  domain: "yourcompany.com",
});

console.log(domain.verificationRecords);
// → returns the DNS records you need to add

LobsterMail generates the verification records specific to your domain. You'll get three records: a TXT record for domain ownership verification, an SPF record, and a CNAME for DKIM signing.

Step 2: add the DNS records#

Head to your DNS provider (Cloudflare, Namecheap, Route 53, GoDaddy — wherever you manage your domain) and add the following records.

Domain verification (TXT):

Type:  TXT
Host:  _lobstermail.yourcompany.com
Value: lobstermail-verify=lm_abc123def456
TTL:   3600

SPF record (TXT):

If you don't have an existing SPF record, add this one:

Type:  TXT
Host:  yourcompany.com
Value: v=spf1 include:spf.lobstermail.ai ~all
TTL:   3600

If you already have an SPF record (for example, from Google Workspace or Microsoft 365), add the LobsterMail include to your existing record. Each domain can only have one SPF record — multiple records will cause authentication to fail.

# Before:
v=spf1 include:_spf.google.com ~all

# After:
v=spf1 include:_spf.google.com include:spf.lobstermail.ai ~all

DKIM record (CNAME):

Type:  CNAME
Host:  lobstermail._domainkey.yourcompany.com
Value: lobstermail._domainkey.lobstermail.ai
TTL:   3600

DKIM adds a cryptographic signature to every email your agent sends. Receiving servers use this to verify the message wasn't altered in transit. LobsterMail uses 2048-bit keys and handles key rotation automatically.

Step 3: verify and activate#

Once your DNS records propagate (usually a few minutes, sometimes up to 48 hours), verify the domain:

const status = await client.domains.verify("yourcompany.com");

console.log(status);
// → { verified: true, spf: "pass", dkim: "pass" }

When verification passes, your agents can immediately start sending from any address on that domain.

Step 4: set up DMARC (recommended)#

DMARC ties SPF and DKIM together and tells receiving servers what to do with messages that fail authentication. It's not strictly required, but it's strongly recommended — especially after Google, Yahoo, and Microsoft made DMARC mandatory for bulk senders.

Type:  TXT
Host:  _dmarc.yourcompany.com
Value: v=DMARC1; p=none; rua=mailto:dmarc-reports@yourcompany.com
TTL:   3600

Start with p=none to monitor without blocking any messages. Once you've confirmed everything is working, move to p=quarantine and eventually p=reject for full protection.

The multi-agent-per-domain pattern#

Here's where custom domains get really powerful. One verified domain can serve as many agents as you need. Each agent gets its own address on your domain, its own shell, and its own purpose.

// Support agent
const supportInbox = await client.provision({
  name: "support",
  domain: "yourcompany.com",
  // → support@yourcompany.com
});

// Billing agent
const billingInbox = await client.provision({
  name: "billing",
  domain: "yourcompany.com",
  // → billing@yourcompany.com
});

// Sales agent
const salesInbox = await client.provision({
  name: "sales",
  domain: "yourcompany.com",
  // → sales@yourcompany.com
});

Three agents, three addresses, one domain. Customers email support@yourcompany.com for help, billing@yourcompany.com for invoices, and sales@yourcompany.com for pricing. Each agent handles its own shell independently, but they all send from your brand.

This pattern scales cleanly. Add a new agent, provision a new address. No additional DNS configuration needed — the domain is already verified and authenticated. Your reef grows without extra overhead.

For more on how agents coordinate across addresses, check out webhooks vs polling for agent email.

What about existing email on the domain?#

If you already use yourcompany.com for regular email (Google Workspace, Microsoft 365, etc.), adding LobsterMail won't interfere with your existing setup. LobsterMail only handles mail sent to addresses provisioned through the platform. Emails to ceo@yourcompany.com still route through your existing provider.

Just make sure you update your SPF record to include both providers (as shown above) rather than creating a second SPF record. One SPF record per domain — that's a hard rule.

From @getlobstermail.com to your own reef#

The path is straightforward: start on the free tier with your-agent@getlobstermail.com, prove out your use case, then molt up to Builder and connect your own domain. Your agent's address changes, but the SDK calls stay the same. The transition is seamless.

If you're comparing options, we broke down how LobsterMail stacks up against AgentMail — including how each platform handles custom domains.

Custom domains aren't just a vanity feature. They're the difference between an agent that feels like a tool and one that feels like part of your team.

Give your agent its own email. Get started with LobsterMail — it's free.