Best Practices Guide

Overview

This guide covers the patterns and strategies that high-performing SmartLead integrations use in production. Whether you’re building a custom outreach tool, syncing with your CRM, or automating campaign management, these best practices will help you get better results and avoid common pitfalls.

Deliverability Best Practices

Deliverability is the foundation of cold email. If your emails land in spam, nothing else matters.

Warm Up Every Account

Never send campaign emails from an account that hasn’t been warmed up for at least 14 days. For new domains, allow 21–30 days.

Python

# When creating an account, always enable warmup
account_payload = {
    "from_name": "Sarah Johnson",
    "from_email": "sarah@yourcompany.com",
    "smtp_host": "smtp.yourprovider.com",
    "smtp_port": 587,
    "imap_host": "imap.yourprovider.com",
    "imap_port": 993,
    "max_email_per_day": 40,
    "warmup_enabled": True,
    "total_warmup_per_day": 25,
    "daily_rampup": 2,
    "reply_rate_percentage": 30
}

Configure DNS Records

Before sending any emails, ensure these DNS records are properly set up for every sending domain:

Record	What It Does	Priority
SPF	Authorizes which servers can send email from your domain	Required
DKIM	Adds a cryptographic signature to verify email authenticity	Required
DMARC	Defines how receivers handle SPF/DKIM failures	Required
Custom Tracking Domain	Uses your domain for open/click tracking links	Recommended

Missing DNS records is the most common cause of deliverability issues. Set these up before enabling warmup — warming up an account with bad DNS records can actively harm your domain reputation.

Rotate Multiple Accounts

Use 3–5 email accounts per campaign to distribute sending volume and reduce the risk of any single account being flagged:

Python

# Link multiple accounts to a campaign
response = requests.post(
    f"{BASE_URL}/campaigns/{campaign_id}/email-accounts",
    params={"api_key": API_KEY},
    json={"email_account_ids": [101, 102, 103, 104, 105]}
)

Monitor Bounce Rates

Set up automated monitoring and pause campaigns if bounce rates spike:

Python

def check_campaign_health(campaign_id):
    """Monitor campaign health and alert on issues."""
    response = requests.get(
        f"{BASE_URL}/campaigns/{campaign_id}/analytics",
        params={"api_key": API_KEY}
    )
    analytics = response.json()

    total_sent = analytics.get("total_sent", 0)
    total_bounced = analytics.get("total_bounced", 0)

    if total_sent > 0:
        bounce_rate = total_bounced / total_sent
        if bounce_rate > 0.05:  # 5% threshold
            print(f"WARNING: Bounce rate {bounce_rate:.1%} — consider pausing campaign")
            # Optionally auto-pause
            requests.post(
                f"{BASE_URL}/campaigns/{campaign_id}/status",
                params={"api_key": API_KEY},
                json={"status": "PAUSED"}
            )

Personalization Best Practices

Use Custom Fields Extensively

Generic cold emails get ignored. Use custom fields to make every email feel hand-written:

Python

lead = {
    "email": "alex@company.com",
    "first_name": "Alex",
    "company_name": "Acme Corp",
    "custom_fields": {
        "job_title": "VP of Sales",
        "industry": "B2B SaaS",
        "pain_point": "low reply rates on outbound",
        "mutual_connection": "Jordan at YC",
        "recent_news": "Series B announcement",
        "team_size": "50"
    }
}

Then reference them in your sequences:

Hi {{first_name}},

Congrats on {{recent_news}} — exciting times at {{company_name}}.

Given your role as {{job_title}}, I imagine {{pain_point}} is something you're thinking about.

{{mutual_connection}} mentioned you might be open to exploring new approaches...

Validate Personalization Data

Always validate custom fields before import to prevent sending emails with empty placeholders:

Python

def validate_lead_personalization(lead, required_fields):
    """Ensure all required personalization fields are present."""
    missing = []
    for field in required_fields:
        if field in ["first_name", "last_name", "email", "company_name"]:
            if not lead.get(field):
                missing.append(field)
        else:
            if not lead.get("custom_fields", {}).get(field):
                missing.append(field)
    return missing

# Check before import
required = ["first_name", "company_name", "job_title", "industry"]
for lead in lead_list:
    missing = validate_lead_personalization(lead, required)
    if missing:
        print(f"Lead {lead['email']} missing: {', '.join(missing)}")

If a custom field might be empty for some leads, write your email copy to handle it gracefully. Instead of “I noticed is hiring,” use “I noticed your team is growing” as a fallback.

Campaign Architecture

Structure Campaigns by Segment

Create separate campaigns for each ICP segment rather than one massive campaign:

Campaign: Q1 SaaS — VP Sales — US (50-200 employees)
Campaign: Q1 SaaS — VP Sales — US (200-500 employees)
Campaign: Q1 SaaS — Head of Growth — US
Campaign: Q1 Fintech — VP Sales — US

This lets you tailor sequences, measure performance by segment, and adjust strategy independently.

Sequence Design

Follow these guidelines for high-performing sequences:

Step	Timing	Purpose	Length
Email 1	Day 0	Hook — introduce your value prop	50-80 words
Email 2	Day 3	Social proof — share a case study	40-70 words
Email 3	Day 7	New angle — different pain point	40-60 words
Email 4	Day 14	Break-up — final follow-up	30-50 words

Python

sequences = {
    "sequences": [
        {"seq_number": 1, "seq_delay_details": {"delay_in_days": 0}, ...},
        {"seq_number": 2, "seq_delay_details": {"delay_in_days": 3}, ...},
        {"seq_number": 3, "seq_delay_details": {"delay_in_days": 4}, ...},
        {"seq_number": 4, "seq_delay_details": {"delay_in_days": 7}, ...}
    ]
}

A/B Test Systematically

Test one variable at a time and run tests until you have statistical significance:

Python

# Test subject lines on step 1
sequence_step = {
    "seq_number": 1,
    "subject": "Quick question about {{company_name}}",
    "email_body": "...",
    "variants": [
        {
            "subject": "{{first_name}}, thought on {{company_name}}'s outbound",
            "email_body": "...",  # Same body to isolate subject impact
            "variant_distribution": 50
        }
    ]
}

Wait for at least 200 sends per variant before drawing conclusions. Small sample sizes produce unreliable results.

Scaling Best Practices

Batch All Operations

Always use batch endpoints when working with multiple items:

Python

# Import leads in batches of 400
batch_size = 400
for i in range(0, len(all_leads), batch_size):
    batch = all_leads[i:i + batch_size]
    result = make_request("POST", f"campaigns/{campaign_id}/leads", {
        "lead_list": batch,
        "settings": {
            "ignore_global_block_list": False,
            "ignore_unsubscribe_list": False,
            "ignore_duplicate_leads_in_other_campaign": False
        }
    })
    time.sleep(1)  # Brief pause between batches

Use Webhooks for Real-Time Data

Don’t poll the API for updates. Set up webhooks and react to events:

Python

# Register webhook once
make_request("POST", "webhooks", {
    "webhook_url": "https://yourapp.com/hooks/smartlead",
    "event_types": ["EMAIL_REPLIED", "EMAIL_BOUNCED", "LEAD_UNSUBSCRIBED"],
    "is_active": True
})

Cache Static Data

Cache data that rarely changes to minimize API calls:

Python

# Cache campaign list (changes infrequently)
campaigns = cached_request("campaigns/", ttl_seconds=300)

# Cache email accounts (changes infrequently)
accounts = cached_request("email-accounts", ttl_seconds=600)

# Don't cache analytics (changes with every send)
analytics = make_request("GET", f"campaigns/{cid}/analytics")

Security Best Practices

Protect Your API Key

Python

# Good: Environment variable
API_KEY = os.getenv("SMARTLEAD_API_KEY")

# Bad: Hardcoded in source
API_KEY = "sl_abc123..."  # Never do this

Never commit API keys to version control, include them in client-side code, or share them in Slack messages. Use environment variables or a secrets manager like AWS Secrets Manager, HashiCorp Vault, or Doppler.

Validate Webhook Sources

Verify that incoming webhooks actually come from SmartLead:

Python

import hmac
import hashlib

def verify_webhook(payload, signature, secret):
    """Verify webhook signature to prevent spoofing."""
    expected = hmac.new(
        secret.encode(),
        payload.encode(),
        hashlib.sha256
    ).hexdigest()
    return hmac.compare_digest(expected, signature)

@app.route('/webhooks/smartlead', methods=['POST'])
def handle_webhook():
    signature = request.headers.get('X-Smartlead-Signature', '')
    if not verify_webhook(request.data.decode(), signature, WEBHOOK_SECRET):
        return jsonify({'error': 'Invalid signature'}), 401

    # Process webhook...

Use Least-Privilege Access

If you have multiple integrations, create separate API keys for each with appropriate access scopes. Rotate keys periodically and revoke unused keys.

Production Checklist

Before going live, verify:

DNS records configured

SPF, DKIM, and DMARC are set up for all sending domains.

Accounts warmed up

All email accounts have been warming for 14+ days with good inbox placement.

Error handling in place

Your integration handles 400, 401, 404, 429, and 500 errors gracefully with retries.

Rate limiting implemented

Client-side rate limiting prevents 429 errors. Webhooks replace polling where possible.

Monitoring active

Bounce rates, reply rates, and campaign health are monitored with alerts.

API key secured

Keys stored in environment variables or secrets manager. Never in source code.

Webhook endpoint tested

Webhook handler processes all event types, returns 200, and handles duplicates.

Lead data validated

All leads are email-verified and personalization fields are validated before import.

What’s Next?

Getting Started Guide

Build your first campaign from scratch

API Reference

Explore all available endpoints

Error Handling

Comprehensive error handling patterns

Rate Limits

Optimize your request patterns

Get Started

Core Concepts

Guides

Overview

Deliverability Best Practices

Warm Up Every Account

Configure DNS Records

Rotate Multiple Accounts

Monitor Bounce Rates

Personalization Best Practices

Use Custom Fields Extensively

Validate Personalization Data

Campaign Architecture

Structure Campaigns by Segment

Sequence Design

A/B Test Systematically

Scaling Best Practices

Batch All Operations

Use Webhooks for Real-Time Data

Cache Static Data

Security Best Practices

Protect Your API Key

Validate Webhook Sources

Use Least-Privilege Access

Production Checklist

What’s Next?

Getting Started Guide

API Reference

Error Handling

Rate Limits

Get Started

Core Concepts

Guides

​Overview

​Deliverability Best Practices

​Warm Up Every Account

​Configure DNS Records

​Rotate Multiple Accounts

​Monitor Bounce Rates

​Personalization Best Practices

​Use Custom Fields Extensively

​Validate Personalization Data

​Campaign Architecture

​Structure Campaigns by Segment

​Sequence Design

​A/B Test Systematically

​Scaling Best Practices

​Batch All Operations

​Use Webhooks for Real-Time Data

​Cache Static Data

​Security Best Practices

​Protect Your API Key

​Validate Webhook Sources

​Use Least-Privilege Access

​Production Checklist

​What’s Next?

Getting Started Guide

API Reference

Error Handling

Rate Limits

Overview

Deliverability Best Practices

Warm Up Every Account

Configure DNS Records

Rotate Multiple Accounts

Monitor Bounce Rates

Personalization Best Practices

Use Custom Fields Extensively

Validate Personalization Data

Campaign Architecture

Structure Campaigns by Segment

Sequence Design

A/B Test Systematically

Scaling Best Practices

Batch All Operations

Use Webhooks for Real-Time Data

Cache Static Data

Security Best Practices

Protect Your API Key

Validate Webhook Sources

Use Least-Privilege Access

Production Checklist

What’s Next?