How To Check SMTP Logs in Windows Server (IIS)?

Problem

Sometimes you cannot send out emails with Microsoft local SMTP Service (127.0.0.1) in your ASP.NET codes.

Solution

You can check the SMTP logs to see what happens. Please follow these steps to setup and check SMTP log files.

a. Enable SMTP Logs

Open Start > Programs > Administrative Tools > Internet Information Service (IIS) Manager. Right click "Default SMTP Virtual Server" and choose "Properties". Check "Enable logging".

Click "Properties ..." to check all options.

b. Check SMTP Logs

You can check the SMTP log files at C:\WINDOWS\system32\LogFiles\SMTPSVC1.

c. Understand SMTP logs

You can open the log file and check the email logs. The most important field is status code. "250" means ok.

Here are the meaning of SMTP status codes.

Status Code Description
211 System status, or system help reply
214 Help message
220 Service ready 
221 Service closing transmission channel 
250 Requested mail action okay, completed 
251 User not local; will forward to 
354 Start mail input; end with "."
421 Service not available, closing transmission channel
450 Requested mail action not taken: mailbox unavailable
451 Requested action aborted: local error in processing
452 Requested action not taken: insufficient system storage
500 Syntax error, command unrecognized
501 Syntax error in parameters or arguments
502 Command not implemented
503 Bad sequence of commands
504 Command parameter not implemented
550 Requested action not taken: mailbox unavailable
551 User not local; please try <....>
552 Requested mail action aborted: exceeded storage allocation
553 Requested action not taken: mailbox name not allowed
554 Transaction failed

Other Resources

  1. Microsoft Exchange Server 2003 - How to understand SMTP Logs in IIS
  2. Enhanced Mail System Status Codes

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