Skip to content
Tomba home
Start free

// formulas and metrics

Unsubscribe Rate

GlossaryFormulas and metricsUpdated March 23, 2026

Definition
The percentage of email recipients who opt out of receiving future communications after opening an email.

Unsubscribe rate is a key email marketing metric that measures the percentage of recipients who click the unsubscribe link after receiving an email. It is calculated by dividing the number of unsubscribes by the number of emails delivered, then multiplying by 100. A healthy unsubscribe rate for B2B emails typically falls below 0.5%, though this varies by industry and email type.

Tracking unsubscribe rates provides valuable insight into audience satisfaction and content relevance. A sudden spike in unsubscribes often indicates that email frequency is too high, content is not relevant, or the audience was not properly targeted. Consistently high unsubscribe rates can damage sender reputation, leading to deliverability issues that affect all future campaigns.

For B2B sales teams conducting cold outreach, managing unsubscribe rates is especially important. Personalizing messages based on the prospect's industry, role, and pain points also keeps unsubscribe rates low by making each email feel relevant and valuable.

Key Points

  • Unsubscribe rate measures the percentage of recipients who opt out of future emails
  • High unsubscribe rates signal content relevance issues and can harm sender reputation
  • Well-targeted, personalized emails to verified addresses keep unsubscribe rates low

Best Practices

  • Monitor unsubscribe rates for every campaign and investigate spikes immediately
  • Segment your email lists to ensure recipients only receive content relevant to their interests

Free Tools

// 02 · in practice with tomba

The API calls behind this term

Size a domain before you prospect it: Email Count returns how many addresses Tomba holds for it, by department and seniority.

GET/email-count1 email count credit

// quick start

Make your first call in a minute

Free account, real API key, the same endpoints Enterprise customers use.

  1. 1Create a free account25 searches a month. No card.
  2. 2Copy your key and secretFrom API keys in the dashboard.
  3. 3Call the APIPaste the request; the answer is JSON.
Get free API keyRead the docs
curl "https://api.tomba.io/v1/email-finder?domain=piedpiper.com&first_name=Richard&last_name=Hendricks" \
  -H "X-Tomba-Key: $TOMBA_API_KEY" \
  -H "X-Tomba-Secret: $TOMBA_SECRET_KEY"
Response
200 OK· 1 search credit
{
  "data": {
    "email": "richard@piedpiper.com",
    "first_name": "Richard",
    "last_name": "Hendricks",
    "full_name": "Richard Hendricks",
    "website_url": "piedpiper.com",
    "company": "Pied Piper",
    "pattern": "{first}",
    "department": "executive",
    "type": "personal",
    "position": "CEO",
    "country": "US",
    "gender": "male",
    "twitter": null,
    "linkedin": "https://www.linkedin.com/in/richard-hendricks",
    "score": 100,
    "accept_all": false,
    "phone_number": true,
    "verification": {
      "date": "2025-01-15T10:32:00+01:00",
      "status": "valid"
    },
    "sources": [
      {
        "uri": "https://piedpiper.com/blog/engineering",
        "website_url": "piedpiper.com",
        "extracted_on": "2024-06-01T09:14:07+01:00",
        "last_seen_on": "2025-01-10T17:02:44+01:00",
        "still_on_page": true
      }
    ],
    "phone_data": []
  }
}