How do I set up email signatures for my agent?

The short answer

Append an HTML signature block to every outbound email’s html field. Build a reusable function that takes agent name, role, and company info, then call it before every messages.send(). Include an AI disclosure line — recipients should know when they are communicating with an agent.

Why agents need signatures

A signature is not decoration. It serves three purposes:

Identity. Recipients need to know who (or what) they are talking to. An agent named “Aria” that signs emails as “Aria, Support Agent at Acme” builds familiarity across a conversation thread.
Legal compliance. Many jurisdictions require business emails to include company name, registration number, and physical address. The EU’s eCommerce Directive and CAN-SPAM both mandate sender identification.
Trust and AI disclosure. Recipients increasingly expect transparency about AI-generated communication. A clear “This email was composed by an AI agent” line prevents confusion and builds trust. Some industries (financial services, healthcare) are moving toward mandatory AI disclosure requirements.

Building a signature template

Create a function that returns the signature HTML. Call it in every send path so the signature is consistent across all agent emails.

interface SignatureParams {
  agentName: string;
  agentRole: string;
  companyName: string;
  companyUrl: string;
  companyAddress?: string;
  logoUrl?: string;
}

function agentSignature(params: SignatureParams): string {
  const logo = params.logoUrl
    ? `<img src="${params.logoUrl}" alt="${params.companyName}" style="height: 32px; margin-bottom: 12px;" /><br />`
    : '';

  const address = params.companyAddress
    ? `<p style="font-size: 12px; color: #999; margin: 4px 0;">${params.companyAddress}</p>`
    : '';

  return `
    <div style="margin-top: 32px; padding-top: 16px; border-top: 1px solid #e5e5e5; font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;">
      ${logo}
      <p style="font-size: 14px; color: #1a1a1a; margin: 0;">
        <strong>${params.agentName}</strong>
      </p>
      <p style="font-size: 13px; color: #666; margin: 4px 0;">
        ${params.agentRole} &middot;
        <a href="${params.companyUrl}" style="color: #2563eb; text-decoration: none;">${params.companyName}</a>
      </p>
      ${address}
      <p style="font-size: 11px; color: #aaa; margin: 12px 0 0 0; font-style: italic;">
        This email was composed by an AI agent. Reply normally — a human can review at any time.
      </p>
    </div>
  `;
}

def agent_signature(
    agent_name: str,
    agent_role: str,
    company_name: str,
    company_url: str,
    company_address: str | None = None,
    logo_url: str | None = None,
) -> str:
    logo = ""
    if logo_url:
        logo = f'<img src="{logo_url}" alt="{company_name}" style="height: 32px; margin-bottom: 12px;" /><br />'

    address = ""
    if company_address:
        address = f'<p style="font-size: 12px; color: #999; margin: 4px 0;">{company_address}</p>'

    return f"""
    <div style="margin-top: 32px; padding-top: 16px; border-top: 1px solid #e5e5e5; font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;">
      {logo}
      <p style="font-size: 14px; color: #1a1a1a; margin: 0;">
        <strong>{agent_name}</strong>
      </p>
      <p style="font-size: 13px; color: #666; margin: 4px 0;">
        {agent_role} &middot;
        <a href="{company_url}" style="color: #2563eb; text-decoration: none;">{company_name}</a>
      </p>
      {address}
      <p style="font-size: 11px; color: #aaa; margin: 12px 0 0 0; font-style: italic;">
        This email was composed by an AI agent. Reply normally — a human can review at any time.
      </p>
    </div>
    """

Using the signature in every send

Wrap your send logic so the signature is always appended. This prevents individual agent actions from forgetting to include it.

const SIGNATURE = agentSignature({
  agentName: 'Aria',
  agentRole: 'Support Agent',
  companyName: 'Acme Inc.',
  companyUrl: 'https://acme.com',
  companyAddress: '123 Market St, San Francisco, CA 94105',
});

async function sendAgentEmail(params: {
  to: string;
  subject: string;
  bodyHtml: string;
  bodyText: string;
  threadId?: string;
  inboxId: string;
  attachments?: string[];
}) {
  await commune.messages.send({
    to: params.to,
    subject: params.subject,
    inboxId: params.inboxId,
    threadId: params.threadId,
    text: params.bodyText + '\n\n--\nAria, Support Agent at Acme Inc.',
    html: params.bodyHtml + SIGNATURE,
    attachments: params.attachments,
  });
}

// Your agent just calls sendAgentEmail — signature is automatic
const replyBody = await llm.generate(conversationHistory);
await sendAgentEmail({
  to: customerEmail,
  subject: `Re: ${originalSubject}`,
  bodyHtml: `<p>${replyBody.replace(/\n/g, '<br />')}</p>`,
  bodyText: replyBody,
  threadId: threadId,
  inboxId: supportInboxId,
});

SIGNATURE = agent_signature(
    agent_name="Aria",
    agent_role="Support Agent",
    company_name="Acme Inc.",
    company_url="https://acme.com",
    company_address="123 Market St, San Francisco, CA 94105",
)

def send_agent_email(
    to: str,
    subject: str,
    body_html: str,
    body_text: str,
    inbox_id: str,
    thread_id: str | None = None,
    attachments: list[str] | None = None,
):
    client.messages.send(
        to=to,
        subject=subject,
        inbox_id=inbox_id,
        thread_id=thread_id,
        text=body_text + "\n\n--\nAria, Support Agent at Acme Inc.",
        html=body_html + SIGNATURE,
        attachments=attachments,
    )

# Your agent just calls send_agent_email — signature is automatic
reply_body = llm.generate(conversation_history)
send_agent_email(
    to=customer_email,
    subject=f"Re: {original_subject}",
    body_html=f"<p>{reply_body.replace(chr(10), '<br />')}</p>",
    body_text=reply_body,
    thread_id=thread_id,
    inbox_id=support_inbox_id,
)

Multi-agent signatures

If you run multiple agents (support, sales, billing), each should have a distinct identity. Store signature config per inbox or per agent role.

const AGENT_SIGNATURES: Record<string, string> = {
  'inb_support_01': agentSignature({
    agentName: 'Aria',
    agentRole: 'Support Agent',
    companyName: 'Acme Inc.',
    companyUrl: 'https://acme.com',
  }),
  'inb_sales_01': agentSignature({
    agentName: 'Marcus',
    agentRole: 'Sales Development',
    companyName: 'Acme Inc.',
    companyUrl: 'https://acme.com',
  }),
  'inb_billing_01': agentSignature({
    agentName: 'Nova',
    agentRole: 'Billing Agent',
    companyName: 'Acme Inc.',
    companyUrl: 'https://acme.com',
  }),
};

function getSignature(inboxId: string): string {
  return AGENT_SIGNATURES[inboxId] ?? AGENT_SIGNATURES['inb_support_01'];
}

AGENT_SIGNATURES = {
    "inb_support_01": agent_signature(
        agent_name="Aria",
        agent_role="Support Agent",
        company_name="Acme Inc.",
        company_url="https://acme.com",
    ),
    "inb_sales_01": agent_signature(
        agent_name="Marcus",
        agent_role="Sales Development",
        company_name="Acme Inc.",
        company_url="https://acme.com",
    ),
    "inb_billing_01": agent_signature(
        agent_name="Nova",
        agent_role="Billing Agent",
        company_name="Acme Inc.",
        company_url="https://acme.com",
    ),
}

def get_signature(inbox_id: str) -> str:
    return AGENT_SIGNATURES.get(inbox_id, AGENT_SIGNATURES["inb_support_01"])

Best practices

Do:

Include agent name and role so recipients build familiarity
Add a one-line AI disclosure — builds trust and may be legally required
Include company name, website, and physical address for CAN-SPAM compliance
Use a system font stack — web fonts do not work in email clients
Keep the signature under 6 lines — long signatures annoy recipients
Use the same signature within a thread — switching signatures mid-conversation is confusing

Don’t:

Embed large images — they trigger spam filters and slow load times
Use <style> tags — Gmail and Outlook strip them (use inline styles)
Include social media icons as base64 data URIs — many clients block these
Add “Sent from my AI” as a P.S. — make it part of the structured signature instead
Put the disclosure in 6px font — that defeats the purpose

The AI disclosure line

This is the most important part of an agent signature. Here are three patterns ranging from minimal to explicit:

Minimal:    "AI-assisted reply"
Standard:   "This email was composed by an AI agent."
Explicit:   "This email was composed by an AI agent. Reply normally — a human can review at any time."

The “explicit” pattern is recommended. It tells the recipient three things: this is AI-generated, they can reply naturally, and a human is available. That is the right balance of transparency and reassurance.

Sending HTML Emails

Format agent emails with HTML — inline styles, templates, and responsive design.

Per-Agent Inboxes

Give each agent its own inbox for identity isolation and reply routing.

Spam Prevention

How signatures and sender identity affect deliverability scores.

Overview

Getting Started

Sending & Composing

Deliverability

Inbound & Threading

Operations

Security & Compliance

Framework Integrations

How do I set up email signatures for my agent?

The short answer

Why agents need signatures

Building a signature template

Using the signature in every send

Multi-agent signatures

Best practices

The AI disclosure line

Sending HTML Emails

Per-Agent Inboxes

Spam Prevention

​The short answer

​Why agents need signatures

​Building a signature template

​Using the signature in every send

​Multi-agent signatures

​Best practices

​The AI disclosure line

​Related

Sending HTML Emails

Per-Agent Inboxes

Spam Prevention

The short answer

Why agents need signatures

Building a signature template

Using the signature in every send

Multi-agent signatures

Best practices

The AI disclosure line

Related