When does SF detect that recipients are u
Printed From: LogSat Software
Category: Spam Filter ISP
Forum Name: Spam Filter ISP Support
Forum Description: General support for Spam Filter ISP
URL: https://www.logsat.com/spamfilter/forums/forum_posts.asp?TID=5312
Printed Date: 31 July 2025 at 2:44am
Topic: When does SF detect that recipients are u
Posted By: pcmatt
Subject: When does SF detect that recipients are u
Date Posted: 22 August 2005 at 3:55pm
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I only see two or three entries in a day for "... was returned to sender - The following recipients are unknown: ..." Meanwhile hundreds of emails to bogus email addresses appear to get sent to my servers each day. When and does SpamFilter validate the recipient email address and are my results normal? Is there something special needed to support this on my receiving email servers? Thanks. ------------- -Matt R |
Replies:
Posted By: LogSat
Date Posted: 26 August 2005 at 11:13am
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Matt, Sorry for the delay, this post slipped thru the cracks.. SpamFilter will log that message (and send an NDR bounce to the sender) when it accepts an email for delivery (thus passes all filters) and tries to forward it to your SMTP server. If during this process, when SpamFilter sends the RCPT TO command to your server, and your server rejects the command/recipient with an error code, then SpamFilter will "flag" the failed recipient and is forced to send an NDR bounce to them to let them know that the email was not delivered. ------------- Roberto Franceschetti http://www.logsat.com" rel="nofollow - LogSat Software http://www.logsat.com/sfi-spam-filter.asp" rel="nofollow - Spam Filter ISP |
Posted By: pcmatt
Date Posted: 26 August 2005 at 12:26pm
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Thanks. The symptom I'm having is that SpamFilter is not logging this unless the receiving SMTP server returns a 550 SMTP error. If the receiver issues a "550" or "unknown user" error SpamFilter correctly writes two log entries (there are two): ...Some recipients do not exist, sending NDR bounce to sender and EMail from: mailto:whateversender@domain.com - whateversender@domain.com to: invalidrecipient @otherdomain.com was returned to sender - The following recipients are unknown: mailto:invalidrecipient@otherdomain.com - invalidrecipient@otherdomain.com If the receiving SMTP server responds with anything else the NDR is sent correctly but nothing is logged by SpamFilter. For example, when my server rejects the rcpt to: command with a 501 5.5.4 Invalid Address the NDR is sent, but nothing logged by SpamFilter It appears that SpamFilter only logs this event properly when a SPECIFIC error code is given to it from the receiver. SpamFilter SHOULD log this when ANY 500 series or permanent error is given on the rcpt to: SMTP command by the receiver. This is important so that we know which recipients were not delivered by reviewing the logs. Thanks again. ------------- -Matt R |
Posted By: LogSat
Date Posted: 26 August 2005 at 1:00pm
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Matt, Is there any way we can access (telnet to the SMTP port) your receiving SMTP server? From our tests all the 500 errors do cause SpamFilter to both send an NDR and log the entries. If we can actually replicate this by seing what your SMTP server replies back with (and if it disconnects us right away or not) we can then troubleshoot it. ------------- Roberto Franceschetti http://www.logsat.com" rel="nofollow - LogSat Software http://www.logsat.com/sfi-spam-filter.asp" rel="nofollow - Spam Filter ISP |
Posted By: pcmatt
Date Posted: 26 August 2005 at 1:09pm
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Email me your Public IP so I can add to our list of allowed IP connections. ------------- -Matt R |
Posted By: pcmatt
Date Posted: 01 September 2005 at 10:11pm
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Wondering how you did on those tests while we had opened IP? You've probably been busy detecting and blocking worm infected networks like the rest of us ------------- -Matt R |
