Error 550: Message Rejected is a common SMTP error indicating an email failed to send due to server rejection. Causes include invalid recipient addresses, blacklisted IPs, misconfigured DNS settings, or spam-like content. Solutions involve verifying email addresses, checking server configurations, and ensuring compliance with anti-spam policies. Resolving this error typically requires troubleshooting both technical and content-related factors.
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What Are the Most Common Triggers for Error 550?
Key triggers include: (1) Invalid or deactivated recipient emails, (2) Sender IP/domain blacklisting, (3) Missing SPF/DKIM/DMARC records, (4) Suspicious content flagged as spam, and (5) Exceeding recipient server rate limits. For example, sending bulk emails without proper authentication often results in 550 errors due to spam filters.
Invalid recipient addresses account for nearly 40% of Error 550 cases. This often occurs when senders use outdated contact lists or mistype domain names (e.g., “gmail.cmo” instead of “gmail.com”). Blacklisted IPs are another major factor—email services like Gmail automatically block messages from IPs flagged in databases like Barracuda Reputation Block List. A lesser-known trigger is temporary domain expiration; if the recipient’s domain registration lapses even briefly, emails to that domain will bounce with 550 errors until DNS records are restored.
| Trigger | Detection Tool | Fix Timeline |
|---|---|---|
| Blacklisted IP | MXToolbox Blacklist Check | 2-48 hours |
| Missing SPF Record | DNS Checker | Immediate after update |
| Rate Limit Exceeded | Server Log Analysis | 24-hour cooldown |
How to Troubleshoot Error 550 Step-by-Step?
1. Verify recipient email address validity. 2. Check sender IP/domain blacklist status using tools like MXToolbox. 3. Ensure SPF/DKIM/DMARC records are correctly configured. 4. Review email content for spam triggers (e.g., excessive links). 5. Test with alternative email clients or servers. 6. Contact the recipient’s IT team to confirm server-side restrictions.
Begin by isolating the issue—send test emails to different addresses to determine if the problem is recipient-specific or systemic. For domain authentication failures, use dig commands to verify TXT records contain correct syntax. Example: dig TXT example.com should return your SPF policy. If content is flagged as spam, tools like Mail-Tester provide granular spam score breakdowns, highlighting problematic phrases or HTML elements. For persistent blacklisting, submit delisting requests through services like Spamhaus while simultaneously rotating to a clean IP address.
“Error 550 often stems from overlooked authentication protocols. A 2023 study showed 68% of 550 cases resolve after implementing DKIM and DMARC. Always validate DNS settings before scaling email campaigns—tools like Dmarcian simplify compliance.” — Email Deliverability Expert, Messaging Industry Association
FAQs
- Q: Can Error 550 be caused by the recipient’s inbox being full?
- A: No—Error 550 relates to rejection by the server, not mailbox storage limits (which trigger errors like 422).
- Q: Does using a VPN increase Error 550 risks?
- A: Yes—VPNs may route emails through blacklisted IPs. Use dedicated email servers for business communication.
- Q: How long does it take to resolve a blacklisting causing Error 550?
- A: Delisting varies by provider—Spamhaus typically processes requests within 24 hours, while ISPs may take 48-72 hours.