Brevo SMTP Relay 535 Authentication Failed

How to fix it

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

1. 1. Use the right credentials

   Copy steps
   1. In Brevo open SMTP & API > SMTP
   2. Copy the login shown there as username
   3. Generate an SMTP key and use it as the password
   Did this fix it? Yes No

2. 2. Use the right host and port

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   1. Host: smtp-relay.brevo.com
   2. Port 587 (STARTTLS), 465 (SSL) or 2525
   3. Do not use port 25
   Did this fix it? Yes No

3. 3. Work around a blocked port

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   1. Test connectivity from the server to the relay
   2. If 587 is blocked by your VPS or host, switch to 2525 or 465
   Did this fix it? Yes No

4. 4. Check activation

   1. If you get a permission or not-activated error, contact Brevo support to activate SMTP for the account
   Did this fix it? Yes No

Symptoms

535 Authentication failed, connection refused, TLS handshake error or timeouts when sending through smtp-relay.brevo.com.

Why it happens

• Using the relay hostname as the username
• Using the account password instead of an SMTP key
• Outbound port 587 blocked by host or firewall
• Old smtp.sendinblue.com hostname
• Port 25 (not supported) or a typo in the port
• Account not yet activated for SMTP

This guide also covers

• brevo smtp not working
• brevo smtp 535
• smtp-relay.brevo.com authentication failed
• brevo smtp port
• brevo smtp error

Other Brevo errors

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