SMTP Server Error Logging
Overview
A logging feature has been added to Version 1.6 to help diagnose issues when sending email through your SMTP server.
The log captures detailed information about each email transmission and records any error codes returned
by the SMTP server.
Default Behavior: Logging is disabled by default. No log files are generated unless explicitly enabled.
Enabling Logging
- Locate the desktop icon for
EmailPaystubs.exe.
- Right‑click the icon and select Properties.
- In the Target field, append
-l (lowercase L) immediately after the executable path.
Example:
"C:\DataSoft Bulk Email Paystubs Standard\EmailPaystubs.exe" -l
- Ensure the executable path is enclosed in quotes if the folder name contains spaces.
- Click Apply and then OK to save the changes.
Log File Details
- Location: Same folder as
EmailPaystubs.exe.
- Filename:
EmailPaystubs<date>.log (e.g., EmailPaystubs2025-12-11.log).
- Contents: Timestamp, recipient address, SMTP server response codes, and error messages.
SMTP Error Codes Reference
✅ Success Codes
| Code | Meaning | Action |
|---|
| 220 | Service ready | No action needed |
| 221 | Service closing channel | Normal disconnect |
| 250 | Requested mail action completed | Message delivered successfully |
| 251 | User not local; will forward | Delivery forwarded |
| 252 | Cannot verify user, but will accept | Message accepted; monitor for bounce |
⏳ Temporary Failures (Soft Bounce)
| Code | Meaning | Likely Cause | Recommended Fix |
|---|
| 421 | Service not available | Server busy or offline | Retry later; check server health |
| 450 | Mailbox unavailable | Inbox full or locked | Retry later; recipient clears space |
| 451 | Local error in processing | Server misconfiguration | Retry later; check logs |
| 452 | Insufficient system storage | Quota exceeded | Free space or expand storage |
| 447 | Timeout waiting for response | Network latency | Retry; check connectivity |
❌ Permanent Failures (Hard Bounce)
| Code | Meaning | Likely Cause | Recommended Fix |
|---|
| 500 | Syntax error, command unrecognized | Invalid SMTP command | Verify client syntax |
| 501 | Syntax error in parameters | Malformed address | Correct input format |
| 502 | Command not implemented | Unsupported command | Remove or adjust command |
| 503 | Bad sequence of commands | Wrong order | Fix client logic |
| 504 | Parameter not implemented | Unsupported parameter | Remove or adjust parameter |
| 550 | Mailbox unavailable | User doesn’t exist | Verify recipient address |
| 551 | User not local | Wrong domain | Use correct domain |
| 552 | Exceeded storage allocation | Mailbox full | Recipient clears space |
| 553 | Mailbox name not allowed | Invalid format | Correct address syntax |
| 554 | Transaction failed | Spam filter or policy block | Check content/authentication |
📈 Enhanced Status Codes
| Code | Meaning | Likely Cause | Recommended Fix |
|---|
| 5.1.1 | Bad destination mailbox | User doesn’t exist | Verify recipient |
| 5.2.2 | Mailbox full | Quota exceeded | Recipient clears space |
| 5.3.0 | System not accepting messages | Policy block | Check server configuration |
| 5.4.1 | No answer from host | DNS/routing issue | Verify MX records |
| 5.7.1 | Delivery not authorized | Spam filter or policy rejection | Check SPF/DKIM/authentication |
Practical Troubleshooting
- 4xx errors: Retry later; often temporary.
- 5xx errors: Fix the root cause before resending.
- 421/451: May indicate throttling or rate limits.
- 550/553: Verify recipient address formatting and existence.
- 554: Check for blacklisting, spam filters, or policy violations.
