Brevo Emails Not Delivered, Bounced or Deferred

How to fix it

Try these in order — the most common fix is first.

1. 1. Read the bounce reason

   Copy steps
   1. Open the contact > History
   2. Show details on the bounce event
   Did this fix it? Yes No

2. 2. Know how Brevo retries

   Copy steps
   1. Deferred emails are retried for up to 36 hours
   2. Hard-bounced addresses are never retried
   Did this fix it? Yes No

3. 3. Fix authentication

   1. Authenticate the domain with DKIM and DMARC (Microsoft requires DMARC)
   Did this fix it? Yes No

4. 4. Slow down sends

   1. Spread large API or SMTP sends to avoid 421/451 throttling
   Did this fix it? Yes No

5. 5. Check status and support

   Copy steps
   1. Check Brevo's status page for incidents
   2. If SMTP was suspended, ask support to assess your transactional quality
   Did this fix it? Yes No

Symptoms

Emails stuck as deferred, soft bounced or hard bounced, transactional emails not arriving.

Why it happens

• Recipient server blocks your sender or IP reputation
• Throttling (421, 451 or TS codes)
• Invalid address (hard bounce)
• Authentication failures
• Yahoo/AOL or Microsoft specific filtering
• Suspension of SMTP sending

This guide also covers

• brevo email bounced
• brevo emails not delivered
• brevo soft bounce
• brevo deferred email
• brevo transactional email not received

The same problem in other apps

All notifications, reminders & messages not sending guides →

• MailerLite Emails Going to Spam (MailerLite)
• Mailchimp Emails Going to Spam (Mailchimp)
• Klaviyo Emails Going to Spam (Klaviyo)
• ActiveCampaign Emails Going to Spam (ActiveCampaign)

Other Brevo errors

• Brevo Account Suspended or Under Review
• Brevo Emails Going to Spam
• Brevo Domain Authentication Failed (DKIM, DMARC)
• Brevo SMTP Relay 535 Authentication Failed
• Brevo Daily Sending Limit Reached (300 Emails)
• Brevo Contacts Import Failed
• Brevo Account Not Approved for Sending
• How to Cancel Brevo Subscription