Building an Email Automation Agent: Reading, Classifying, and Responding to Emails

Why Email Still Dominates Business Communication

Despite the rise of Slack, Teams, and dozens of other messaging platforms, email remains the backbone of external business communication. The average knowledge worker receives over 120 emails per day. Most of those emails fall into predictable categories: meeting requests, customer inquiries, status updates, vendor follow-ups, and internal approvals. An AI agent that can read, classify, and draft responses to these messages saves hours of repetitive work every week.

In this guide, we will build a complete email automation agent using Python. The agent connects to an inbox, classifies each message by intent, selects an appropriate response template, and generates a tailored draft. We will use both IMAP for universal mailbox access and the Gmail API for Google Workspace environments.

Connecting to an Inbox with IMAP

IMAP is the universal protocol for reading email. Every major email provider supports it. Python's imaplib handles the connection, and the email module parses message content:

import imaplib
import email
from email.header import decode_header
from dataclasses import dataclass

@dataclass
class ParsedEmail:
    sender: str
    subject: str
    body: str
    date: str
    message_id: str

def connect_and_fetch(
    host: str, username: str, password: str, folder: str = "INBOX", limit: int = 20
) -> list[ParsedEmail]:
    """Connect to an IMAP server and fetch recent unread emails."""
    conn = imaplib.IMAP4_SSL(host)
    conn.login(username, password)
    conn.select(folder)

    status, message_ids = conn.search(None, "UNSEEN")
    ids = message_ids[0].split()[-limit:]

    results = []
    for mid in ids:
        _, msg_data = conn.fetch(mid, "(RFC822)")
        raw = email.message_from_bytes(msg_data[0][1])

        subject, encoding = decode_header(raw["Subject"])[0]
        if isinstance(subject, bytes):
            subject = subject.decode(encoding or "utf-8")

        body = ""
        if raw.is_multipart():
            for part in raw.walk():
                if part.get_content_type() == "text/plain":
                    body = part.get_payload(decode=True).decode("utf-8", errors="replace")
                    break
        else:
            body = raw.get_payload(decode=True).decode("utf-8", errors="replace")

        results.append(ParsedEmail(
            sender=raw["From"],
            subject=subject,
            body=body[:3000],
            date=raw["Date"],
            message_id=raw["Message-ID"],
        ))

    conn.logout()
    return results

The function fetches up to 20 unread messages, parses headers and body text, and returns structured ParsedEmail objects. Truncating the body to 3000 characters keeps LLM token costs reasonable.

Classifying Emails by Intent

Once we have parsed emails, the agent classifies each one. Classification determines which response template to use and whether the email needs human attention:

from openai import OpenAI

CATEGORIES = [
    "meeting_request",
    "customer_inquiry",
    "vendor_followup",
    "status_update",
    "action_required",
    "spam_or_marketing",
    "personal",
]

client = OpenAI()

def classify_email(parsed: ParsedEmail) -> dict:
    """Classify an email into a category with confidence."""
    response = client.chat.completions.create(
        model="gpt-4o-mini",
        temperature=0,
        response_format={"type": "json_object"},
        messages=[
            {
                "role": "system",
                "content": (
                    "You classify emails. Return JSON with keys: "
                    "category (one of: " + ", ".join(CATEGORIES) + "), "
                    "confidence (float 0-1), "
                    "summary (one sentence), "
                    "urgency (low, medium, high)."
                ),
            },
            {
                "role": "user",
                "content": f"From: {parsed.sender}\nSubject: {parsed.subject}\n\n{parsed.body}",
            },
        ],
    )
    import json
    return json.loads(response.choices[0].message.content)

Using response_format={"type": "json_object"} ensures the model returns valid JSON every time. The classification includes a confidence score so the agent can flag uncertain cases for human review.

Generating Draft Responses

With classification complete, the agent generates a draft response. Each category maps to a system prompt that constrains the tone and content:

RESPONSE_PROMPTS = {
    "meeting_request": (
        "Draft a polite reply to this meeting request. "
        "Confirm availability or suggest alternative times. Keep it under 100 words."
    ),
    "customer_inquiry": (
        "Draft a helpful reply to this customer question. "
        "Be professional and thorough. Ask clarifying questions if needed."
    ),
    "vendor_followup": (
        "Draft a brief professional reply acknowledging this vendor message."
    ),
    "action_required": (
        "Draft a reply acknowledging receipt and confirming you will address the request."
    ),
}

def generate_draft(parsed: ParsedEmail, classification: dict) -> str | None:
    """Generate a draft response based on email classification."""
    category = classification["category"]
    if category in ("spam_or_marketing", "status_update", "personal"):
        return None  # No auto-reply for these categories

    system_prompt = RESPONSE_PROMPTS.get(category, RESPONSE_PROMPTS["action_required"])

    response = client.chat.completions.create(
        model="gpt-4o-mini",
        temperature=0.4,
        messages=[
            {"role": "system", "content": system_prompt},
            {
                "role": "user",
                "content": (
                    f"Original email from {parsed.sender}:\n"
                    f"Subject: {parsed.subject}\n\n{parsed.body}"
                ),
            },
        ],
    )
    return response.choices[0].message.content

The agent skips spam, status updates, and personal messages entirely. For everything else, it generates a contextual draft that a human can review before sending.

Saving Drafts via the Gmail API

For Google Workspace users, the Gmail API lets you save drafts directly into the inbox:

import base64
from email.mime.text import MIMEText
from googleapiclient.discovery import build

def save_gmail_draft(service, to: str, subject: str, body: str) -> str:
    """Save a draft reply in Gmail."""
    message = MIMEText(body)
    message["to"] = to
    message["subject"] = f"Re: {subject}"
    raw = base64.urlsafe_b64encode(message.as_bytes()).decode()

    draft = service.users().drafts().create(
        userId="me",
        body={"message": {"raw": raw}},
    ).execute()
    return draft["id"]

Orchestrating the Full Pipeline

The main loop ties everything together, processing each unread email through the classify-then-respond pipeline:

import logging

logging.basicConfig(level=logging.INFO)
logger = logging.getLogger("email_agent")

def run_email_agent(imap_host: str, username: str, password: str):
    """Main loop: fetch, classify, draft responses."""
    emails = connect_and_fetch(imap_host, username, password)
    logger.info(f"Fetched {len(emails)} unread emails")

    for parsed in emails:
        classification = classify_email(parsed)
        logger.info(
            f"[{classification['category']}] {parsed.subject} "
            f"(confidence: {classification['confidence']}, urgency: {classification['urgency']})"
        )

        draft = generate_draft(parsed, classification)
        if draft:
            logger.info(f"  Draft generated ({len(draft)} chars)")
            # save_gmail_draft(service, parsed.sender, parsed.subject, draft)
        else:
            logger.info("  Skipped (no reply needed)")

FAQ

How do I handle emails with attachments?

Extract attachments using part.get_filename() inside the multipart walk loop. Save them to disk or cloud storage, then include a summary of attachment names and types in the classification prompt so the LLM can factor them into its response.

Is it safe to auto-send responses without human review?

Start with draft-only mode where the agent creates drafts for human approval. Once you have validated accuracy over a few hundred emails and the confidence threshold is above 0.9, you can enable auto-send for low-risk categories like meeting confirmations and acknowledgments.

How do I prevent the agent from replying to no-reply addresses?

Add a sender filter that checks for common no-reply patterns like noreply@, no-reply@, and mailer-daemon@. Skip classification entirely for these senders to avoid wasting API calls.

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