Question/Issue
- You receive a Non-Delivery Report (NDR) or bounce-back message after sending an email.
- Common error codes include:
- 550 5.1.1 – Recipient address does not exist
- 552 5.2.3 – Message size exceeds limit
- 554 5.7.1 – Message rejected due to policy or spam filter
- Email remains in the Outbox or shows Delivery Failed status.
Environment
Cause
Bounce-back errors typically occur due to:
- Incorrect recipient email address
- Recipient mailbox full or inactive
- Sender or recipient domain blocked by spam filters
- Message size exceeds organizational or recipient limits
- Authentication or DNS issues (SPF, DKIM, DMARC)
- Temporary server outages or misconfigured mail routing
Resolution
1. Verify Recipient Address
- Double-check spelling and domain (e.g.,
@company.com).
- If unsure, confirm with the recipient or directory lookup.
2. Check Bounce-Back Error Details
- Review the NDR for error codes and diagnostic information.
- Common codes:
- 550 5.1.1 – Invalid recipient
- 552 5.2.3 – Attachment too large
- 554 5.7.1 – Blocked by policy
3. Reduce Message Size
- Compress or remove large attachments.
- Use OneDrive or SharePoint links for file sharing.
4. Validate Your Email Domain
- Ensure SPF, DKIM, and DMARC records are correctly configured.
- Contact IT if you suspect domain reputation issues.
5. Check Spam/Block Lists
- Ask recipient to verify your domain isn’t on their block list.
- If using Outlook, check your own Blocked Senders list.
6. Retry Later
- Temporary server issues can cause bounce-backs.
- Wait 15–30 minutes and resend.
7. Escalate to IT
- If the error persists, provide IT with:
- Full bounce-back message
- Time and recipient details
- Any recent changes to your account or domain