Best practices
Follow these deliverability best practices to ensure your emails reach the inbox
Email deliverability is a shared responsibility. Following these best practices helps protect your sender reputation and ensures your messages reach your audience.
Overview
Good email practices go beyond just having the right content—they also involve how, when, and to whom you send. This guide summarizes essential best practices to improve your deliverability, avoid spam filters, and maintain a healthy sender reputation.
Keep a clean audience
Maintaining good audience hygiene is one of the most impactful things you can do:
- Send only to users who have opted in to receive emails (preferably through double opt-in).
- Remove bounced, fake, or invalid addresses using third-party verification services.
- Regularly clean your list of unengaged recipients (e.g., those who haven’t opened emails in over six months).
- Avoid sending to purchased, rented, or scraped email lists.
For more on this topic, see our Audience Hygiene guide.
Monitor your key metrics
Resend enforces strict thresholds to protect all senders:
- Spam complaint rate: below 0.08%
- Bounce rate: below 4%
Going above these limits can result in account suspension without warning.
To stay compliant:
- Use unsubscribe links (see Unsubscribe guide)
- Honor opt-outs within 7 days
- Remove hard bounces and repeated soft bounces
Warm up your domain gradually
When sending from a new domain or increasing your volume, use a warm-up plan to build your domain reputation:
New domain warm-up schedule
| Day | Max emails/day | Max emails/hour |
|---|---|---|
| 1 | 150 | – |
| 2 | 250 | – |
| 3 | 400 | – |
| 4 | 700 | 50 |
| 5 | 1,000 | 75 |
| 6 | 1,500 | 100 |
| 7 | 2,000 | 150 |
Avoid sudden spikes and monitor bounce/spam rates daily.
For full warm-up guidance, see the Warming Up Guide.
Avoid shortcuts and bad practices
Some tactics may seem tempting, but they can severely damage your sender reputation:
- Do not use third-party warm-up tools that simulate engagement or manipulate anti-spam filters.
- Never spoof sender domains without proper authentication (SPF, DKIM, DMARC).
- Avoid sending repetitive, irrelevant, or misleading content.
Instead, focus on:
- Sending relevant and valuable content that recipients expect.
- Using proper sender authentication for all outbound email.
- Including a visible and functional unsubscribe link in every email.
Stay compliant
To comply with Resend’s Acceptable Use Policy and global regulations:
- Only send to opt-in users
- Include a valid physical address and sender identity
- Explain why you’re contacting the recipient (especially for B2B cold outreach)
- Provide a visible and working unsubscribe option
- Follow laws like CAN-SPAM (U.S.), GDPR (EU), and CASL (Canada)
Summary
Following these practices keeps your domain in good standing and ensures your email campaigns are successful. Respect your users’ consent, monitor your performance, and focus on sustainable engagement. Your reputation—and your deliverability—will thank you.