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Overview

Mailbox Health is a monitoring feature that tracks the status and deliverability of your outbound email mailboxes. It helps ensure your outbound emails reach recipients successfully by monitoring authentication setup, sending reputation, and domain configuration. Maintaining healthy mailboxes is essential for successful email outreach campaigns and sequence performance, as poor mailbox health directly impacts deliverability rates and can lead to emails being marked as spam. Mailbox health monitoring works alongside email verification and sequence performance tracking to provide a complete view of your email outreach effectiveness. Regular maintenance helps protect your sender reputation and ensures consistent campaign results.

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Why Mailbox Health Impacts Deliverability

Mailbox health directly impacts your email outreach success and sender reputation. Healthy mailboxes achieve better inbox placement rates, meaning more of your emails reach recipients’ primary inboxes rather than spam folders. Poor mailbox health can cause emails to be blocked or filtered, reducing campaign effectiveness and potentially damaging your long-term sending reputation. The health monitoring system provides early warnings about deliverability issues before they affect your campaigns, allowing you to take proactive action to maintain consistent outreach performance.

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Accessing Mailbox Health

Mailbox Health appears in two places:

1. Mailboxes list (the Health column) shows a color-coded badge for every mailbox.
   • Navigate to Settings → @ Email Set Up in your account
     1. Admin-level access is required to view health for all mailboxes across the organization. Non-admin users can view health for mailboxes they own.
     2. Select the Mailboxes tab. Locate the Health column
     3. You can filter the list by health status using the Health filter. The available filter options are Satisfactory and Degraded.
     4. Click any mailbox row to open its detail page for the full health breakdown.
        
2. Mailbox health is also visible from within a sequence, so you can monitor the health of mailboxes actively sending for that sequence without leaving the workflow.
   1. Open a sequence and navigate to the Performance tab.
   2. Scroll to the Mailboxes section at the bottom of the Performance tab.
      

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How Reevo Measures and Displays Mailbox Health

Each mailbox receives an overall health status of Satisfactory or Needs attention based on three health factors: engagement metrics, domain health, and warm-up status. Reevo automatically evaluates your mailboxes by looking at aggregate email activity over the most recent 14-day window. If any contributing factor is flagged, the overall status changes to Needs attention so you can investigate before your campaigns are affected.

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Understanding the Health Factor Cards

Below the overall status, you will see up to three expandable cards. Each card represents a factor that contributes to your mailbox’s health. 1. Engagement: evaluates your email engagement metrics over the last 14 days.

• Healthy: “Your engagement metrics are satisfactory.”
• Needs attention: “Some engagement metrics need attention to maintain optimal deliverability.”

Click the card to expand it and see aggregate metrics over 14 days: The engagement factor is marked as Needs attention when any of the following thresholds are exceeded:

• Bounce rate above 5%
• Unsubscribe rate above 1%
• Open rate or reply rate falls below expected levels

Note: At least 50 emails must have been sent before engagement metrics are evaluated. For unsubscribe rate specifically, at least 100 emails are required before that metric is assessed.

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2. Domain health This card shows the health status inherited from your sending domain. It displays a Satisfactory or Needs attention badge alongside a description:

• Healthy: “Domain health status is satisfactory.”
• Needs attention: “Domain health status needs attention.”
• Unavailable: “Domain health status is not available.”

Domain health factors include DNS authentication records (SPF, DKIM, DMARC), domain age and spam blocklist status. A View domain details button lets you navigate directly to the domain’s health page for a deeper breakdown.

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3. Warm-up This card shows the current warm-up status of the mailbox. It displays one of the following states: When expanded, the warm-up card may show additional metrics such as Spam rate (as a percentage) and Active days (number of days the warm-up has been running). Important: Warm-up metrics are informational only. They do not affect the overall mailbox health status. Even if warm-up metrics are flagged, the mailbox will remain Satisfactory as long as engagement and domain health are in good standing.

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Mailbox Health States

The mailbox health system uses five primary health statuses to indicate deliverability performance: The overall status is Needs attention if ANY of the following are true:

• The parent domain’s health status is degraded
• The mailbox’s bounce rate exceeds the threshold
• The open rate is below expected levels
• The reply rate is below expected levels
• The unsubscribe rate exceeds the threshold

The overall status is Satisfactory when all of the above factors are within acceptable ranges. If a factor has insufficient data (for example, fewer than 50 emails sent), it is skipped rather than counted against the mailbox. Additional Detail Page Sections The mailbox detail page also includes:

• Mailbox details (collapsible): Shows basic information including email address, type, domain, first name, last name and owner.
• Sending configuration: Shows warm-up limit, daily send limit with usage progress bar, minimum delay between emails, status, and whether warm-up has been bypassed.
• Sequence usage: Shows which sequences are currently using this mailbox.

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Improving Mailbox Health

If Engagement needs attention The engagement card evaluates bounce rate and unsubscribe rate over the last 14 days. (Open rate and reply rate are shown for reference but do not trigger the “Needs attention” status.) High bounce rate (above 5%):

• Reevo offers email verification as part of our suite of products. Double-check your settings to ensure stricter filtering is enabled. This helps exclude contacts with invalid email addresses upfront, so remaining bounces are more likely caused by domain or IP-level blocks rather than bad addresses.
• Clean your contact lists before launching sequences. Use email verification tools to remove invalid addresses.
• Remove hard bounces and long-term inactive contacts from your lists.
• If bounce rates spike, check your domain against blocklist tools like Spamhaus.

High unsubscribe rate (above 1%, assessed after 100+ emails sent):

• Improve targeting. Match your messaging tone to the persona you’re reaching out to.
• Avoid bait-and-switch subject lines or mismatched copy.
• Segment by role, intent, or behavior rather than blasting a static list.

General engagement best practices:

• Write like a human. Avoid AI-generic or bloated marketing language.
• Personalize deeply with real context (mutual connections, industry events, recent news).
• Use A/B testing to find which subject lines and formats resonate.
• Keep sending volume low (dozens per mailbox, not hundreds) to maintain reputation.

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If Domain health needs attention Click View domain details on the domain health card to see the specific issue. Common causes:

• Missing DNS records (SPF, DKIM, DMARC, MX): If this is an issue, contact Reevo Support
  1. Domains purchased through Reevo (primary, self-serve) - Reevo handles domain registration, DNS configuration (SPF, DKIM, DMARC, MX), and ongoing health monitoring automatically. This is the standard workflow.
  2. Bring your own domain - Customers who purchased a domain from a third-party provider can transfer DNS control to Reevo by updating their nameservers. However, this is not self-serve - it requires contacting a Reevo onboarding specialist or support rep. Once transferred, Reevo manages the DNS records.
• Domain is too new (under 20 days old): New domains are treated with suspicion. Continue warming up and sending at low volumes. Reputation builds over time.
• Listed on spam blocklists: Request delisting from the relevant blocklist provider and investigate what caused the listing.

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Troubleshooting / FAQs