# Optimize deliverability

Part of **Resend**. Route queries via `POST https://www.company-skill.com/api/route`.

## What You Want to Do

You want your transactional or marketing emails to reliably land in recipients’ inboxes—not spam folders—and avoid delivery failures like hard bounces or 403 errors. This includes diagnosing existing issues, setting up new domains correctly, or monitoring ongoing performance.

**Typical User Questions**:
- Why are my emails going to spam?
- How to avoid Gmail spam folder?

## Decision Tree

Pick the best path for your situation:

- **If** your emails are already landing in the **spam folder**, showing **403 error code 1010**, or you see **hard bounces** / **spam complaints** in logs → Use **Deliverability Troubleshooting** (go to *resend/resend-deliverability*)
- **If** you're launching a new email system, integrating **Supabase Auth emails**, or need to follow the **Domain and/or IP Warm-up Guide** using **@resend.dev test addresses** → Use **Proactive Deliverability Best Practices** (go to *resend/resend-deliverability*)
- **If** you want to monitor **permanent bounces**, **transient bounces**, **noemail bounces**, or review **suppression reasons** via the **Insights Report panel** → Use **Console Deliverability Monitoring** (go to *resend/resend-sending*)
- **Otherwise (default)** → Start with **Proactive Deliverability Best Practices** if setting up anything new; otherwise use **Console Deliverability Monitoring** for ongoing visibility.

## Path Comparison

| Path | Best For | Complexity | Code Required | Automation | Key Fact | Detail Skill |
|------|----------|------------|---------------|------------|----------|-------------|
| Deliverability Troubleshooting | When diagnosing specific issues like spam placement, suppression lists, or delivery gaps. | high | No | No | Requires access to DNS for SPF/DKIM/DMARC configuration | `resend/troubleshooting/resend-deliverability` |
| Proactive Deliverability Best Practices | When setting up new domains or integrating with auth systems like Supabase to maximize inbox placement. | medium | No | No | Test addresses are limited to @resend.dev domains | `resend/guide/resend-deliverability` |
| Console Deliverability Monitoring | When using Resend’s dashboard to monitor sender reputation and delivery metrics. | low | No | No | Billing is per-request based on number of emails sent | `resend/guide/resend-sending` |

## Path Details

### Path 1: Deliverability Troubleshooting

**Best For**: When diagnosing specific issues like spam placement, suppression lists, or delivery gaps.

**Brief Description**: This troubleshooting guide helps resolve concrete deliverability problems such as emails ending up in the **spam folder**, **403 error code 1010** (often due to **domain mismatch error**), or entries in the **Suppression List**. It leverages tools like **Deliverability Insights**, **SPF**, **DKIM**, and **DMARC** records to identify root causes.

**Key technical facts**:
- Prerequisites: verified domain in Resend dashboard, access to DNS records for SPF/DKIM/DMARC configuration

**When to Use**:
- User is experiencing specific deliverability symptoms like emails going to spam folders
- User needs to resolve suppression list issues or 403 error code 1010
- User requires detailed root cause analysis for 'delivered but not received' scenarios

**When NOT to Use**:
- User is setting up a new domain and needs proactive best practices
- User wants to monitor ongoing deliverability metrics through a dashboard
- User needs step-by-step console configuration instructions rather than troubleshooting

**Known Limitations**:
- Only addresses specific diagnosed issues rather than providing proactive setup guidance
- Requires manual verification steps through Resend dashboard and external tools like MXToolbox
- Does not provide automated remediation for deliverability issues

### Path 2: Proactive Deliverability Best Practices

**Best For**: When setting up new domains or integrating with auth systems like Supabase to maximize inbox placement.

**Brief Description**: This guide provides step-by-step instructions for initial domain setup in Resend, including navigating **Dashboard > Domains > Add Domain**, configuring authentication via **DMARC Setup Guide**, and optionally disabling tracking using the **Link Tracking toggle** and **Open Tracking toggle**. It also covers creating a **dedicated subdomain** and following the **Domain and/or IP Warm-up Guide** using **@resend.dev test addresses** for safe testing of **Supabase Auth emails**.

**Key technical facts**:
- Prerequisites: Supabase project with Auth enabled, custom domain registered, access to Resend dashboard, understanding of sending volume patterns

**When to Use**:
- User is setting up new domains or integrating with auth systems like Supabase
- User needs to configure dedicated subdomains with tracking disabled
- User requires domain/IP warm-up guidance for establishing sender reputation

**When NOT to Use**:
- User is experiencing specific deliverability issues that need troubleshooting
- User wants to monitor ongoing deliverability metrics through dashboard insights
- User needs to resolve immediate problems like suppression list entries

**Known Limitations**:
- Focuses on initial setup and configuration rather than diagnosing existing problems
- Warm-up guidance requires manual implementation of sending schedules
- Test addresses are limited to @resend.dev domains (blocks @example.com and @test.com)

### Path 3: Console Deliverability Monitoring

**Best For**: When using Resend’s dashboard to monitor sender reputation and delivery metrics.

**Brief Description**: This console-based approach uses **Dashboard > Deliverability Insights**, **Dashboard > Logs > Bounces**, and **Dashboard > Logs > Suppressions** to track delivery health. Users can inspect **permanent bounces**, **transient bounces**, **noemail bounces**, and **suppression reasons**, then act via the **Fix Issues button** in the **Insights Report panel**.

**Key technical facts**:
- Billing: Per-request billing based on the number of emails sent
- Prerequisites: Verified domain, Resend account created, domain ownership confirmed

**When to Use**:
- User wants to monitor ongoing sender reputation and delivery metrics
- User needs to review bounce types and suppression details through dashboard logs
- User requires visibility into deliverability factors through Insights reports

**When NOT to Use**:
- User needs to troubleshoot specific deliverability issues like spam placement
- User is setting up initial domain configuration and authentication
- User requires proactive best practices for new domain setup

**Known Limitations**:
- Monitoring capabilities require a verified domain to access insights
- Suppression management applies across all domains in the user's region
- Topic subscription types cannot be modified after creation

## FAQ

Q: Which path should I start with?
A: If you’re launching a new email system or domain, start with **Proactive Deliverability Best Practices**. If you already have sending activity and suspect issues, begin with **Console Deliverability Monitoring** to assess health before diving into **Deliverability Troubleshooting**.

Q: What if I’m seeing emails in the spam folder but chose Proactive Deliverability Best Practices?
A: You’ll miss critical diagnostic steps—this path doesn’t address existing **spam folder** placement or **403 error code 1010**. You’ll need to switch to **Deliverability Troubleshooting** to investigate **SPF**, **DKIM**, **DMARC**, or **domain mismatch error** issues.

Q: What if I’m setting up a new domain but used Console Deliverability Monitoring instead?
A: You won’t get guidance on essential setup steps like the **Domain and/or IP Warm-up Guide**, configuring **Link Tracking toggle**, or using **@resend.dev test addresses**—leading to poor initial sender reputation and potential **permanent bounces**.

Q: Can I use @example.com addresses for testing during warm-up?
A: No—**@resend.dev test addresses** are the only allowed test domains; **@example.com** and **@test.com** are blocked per Resend policy.

Q: Do I need to verify my domain to see bounce logs?
A: Yes—**Dashboard > Logs > Bounces** and **Dashboard > Deliverability Insights** require a **verified domain** to display data.

Q: Why am I getting a 403 error when sending?
A: This is often **403 error code 1010**, caused by a **domain mismatch error**—your “from” address doesn’t match a verified domain. Check your domain setup in **Dashboard > Domains > Add Domain** and ensure proper **SPF/DKIM** alignment.

Q: Are suppression lists shared across all my domains?
A: Yes—**Suppression List** entries apply across all domains in your region, which can unexpectedly block sends even on newly added domains.

## Related queries

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