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SMTP Bounce Code 5.2.0: Other Mailbox Status

SMTP bounce code 5.2.0 indicates that there is a problem with the recipient's mailbox that doesn't fit into a more specific category. This is a permanent failure (hard bounce), meaning there's a fundamental issue with the mailbox that won't resolve on retry.

What Does 5.2.0 Mean?

The enhanced status code 5.2.0 follows the SMTP Enhanced Status Code format:

  • 5 = Permanent failure (hard bounce)
  • 2 = Mailbox status (related to the recipient's mailbox)
  • 0 = Other or undefined mailbox status

When you receive a 5.2.0 bounce, it means the receiving mail server has identified a mailbox problem that doesn't fall into specific categories like "mailbox disabled" (5.2.1) or "mailbox full" (5.2.2). This is a catch-all code for various mailbox issues.

Bounce Type

  • Type: Hard bounce (permanent failure)
  • Category: Mailbox
  • Action Required: Remove the email address from your mailing list or investigate the specific mailbox issue

Common Causes

  1. Mailbox Configuration Issues: Problems with mailbox configuration that don't match other specific error codes
  2. Mailbox Restrictions: The mailbox has restrictions that prevent delivery
  3. Account Status Issues: The mailbox account has status issues that prevent mail delivery
  4. Virtual Mailbox Problems: Issues with virtual mailbox configurations
  5. Mailbox Policy Violations: The mailbox violates domain policies that prevent delivery
  6. Resource Limitations: Mailbox resource limitations that aren't related to storage quota
  7. Access Restrictions: Access restrictions preventing mail delivery to the mailbox
  8. Mailbox Maintenance: Permanent mailbox maintenance or configuration issues
  9. Account Type Issues: Problems related to the type of account or mailbox setup
  10. Generic Mailbox Error: A mailbox error that doesn't fit into more specific categories

How to Resolve

For Email Marketers

  1. Remove from List: Remove the email address from your active mailing list immediately
  2. Verify Address: Double-check the email address for any obvious issues
  3. Contact Recipient: If possible, contact the recipient through alternative channels to verify their mailbox status
  4. Review Collection Methods: Review how you collected this email address to prevent similar issues
  5. Clean Your List: Regularly clean your email list to remove invalid addresses

For Developers

  1. Validate Email Address: Implement email validation before storing addresses
  2. Implement Bounce Handling: Set up automated bounce processing to remove 5.2.0 bounces from your database
  3. Log Bounce Details: Log the full bounce message to understand the specific mailbox issue
  4. Pattern Analysis: Analyze 5.2.0 bounces to identify patterns and improve validation
  5. Suppression List: Maintain a suppression list of bounced addresses
  6. Use Email Verification Services: Consider using email verification APIs to check addresses before sending

Investigation Steps

When you receive 5.2.0 bounces, investigate:

  1. Check Full Bounce Message: Review the complete bounce message for specific details about the mailbox issue
  2. Validate Address Format: Verify the email address follows proper format
  3. Test Address: Try sending a test email to verify the issue
  4. Review Related Codes: Check if the issue might be better categorized under other mailbox codes (5.2.1, 5.2.2)
  5. Contact Support: If needed, contact the recipient's IT department for more information

Related Bounce Codes

Examples

Example Bounce Message

550 5.2.0 Other mailbox status
Mailbox is not available for message delivery.

Example Enhanced Status Code

550 5.2.0 <[email protected]>: Other mailbox status - mailbox configuration error

Common Email Provider Responses

  • Generic: "550 5.2.0 Other mailbox status"
  • Configuration Error: "Mailbox configuration error"
  • Not Available: "Mailbox is not available for delivery"
  • Status Issue: "Mailbox status prevents delivery"

Best Practices

  1. Never Retry: Don't attempt to resend emails to addresses that bounce with 5.2.0—they will continue to fail
  2. Validate Before Adding: Always validate email addresses before adding them to your mailing list
  3. Maintain List Hygiene: Regularly clean your email list to remove invalid addresses
  4. Investigate Patterns: Analyze 5.2.0 bounces to identify common issues
  5. Log Bounce Details: Keep detailed logs of bounce messages to understand specific issues
  6. Use Suppression Lists: Maintain suppression lists to prevent sending to invalid addresses
  7. Review Related Codes: Check if the issue might be better addressed by reviewing related bounce code documentation