SMTP Error Matrix

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

1. Locate the desktop icon for EmailPaystubs.exe.
2. Right‑click the icon and select Properties.
3. In the Target field, append -l (lowercase L) immediately after the executable path.
   Example:
   "C:\DataSoft Bulk Email Paystubs Standard\EmailPaystubs.exe" -l
4. Ensure the executable path is enclosed in quotes if the folder name contains spaces.
5. 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.