Spam Filter ISP Support Forum

  New Posts New Posts RSS Feed - NDR for unknown user not sent
  FAQ FAQ  Forum Search   Register Register  Login Login

NDR for unknown user not sent

 Post Reply Post Reply
Author
dman3883 View Drop Down
Newbie
Newbie


Joined: 09 September 2008
Status: Offline
Points: 2
Post Options Post Options   Thanks (0) Thanks(0)   Quote dman3883 Quote  Post ReplyReply Direct Link To This Post Topic: NDR for unknown user not sent
    Posted: 09 September 2008 at 5:35pm

When someone sends to an email address that doesn't exist on our mail server, the unknown user NDR is not delivered back to the sender. All other NDR's for rejected emails that trigger the filters are sent.

I can see in the log files that spamfilter is claiming to generate the NDR for the unknown user, but the sender doesn't get it.
 
09/09/08 14:03:06:593 -- (2088) EMail from redacted@somedomain.com to hidden@thisdomain.com --  was forwarded to ***.***.***.***:25
09/09/08 14:03:06:593 -- (2088) Some recipients do not exist, sending NDR bounce to sender
09/09/08 14:03:06:593 -- (2088) EMail from: redacted@somedomain.com to: hidden@thisdomain.com was returned to sender - The following recipients had delivery problems: hidden@thisdomain.com --  --  --  -- The remote server said: -- 550 unknown user <hidden@thisdomain.com> --
 
(actual addresses have been removed from log)
 
Anyone have any idea why? Thanks for the help.
Back to Top
LogSat View Drop Down
Admin Group
Admin Group
Avatar

Joined: 25 January 2005
Location: United States
Status: Offline
Points: 4068
Post Options Post Options   Thanks (0) Thanks(0)   Quote LogSat Quote  Post ReplyReply Direct Link To This Post Posted: 09 September 2008 at 9:47pm
dman3883,

SpamFilter will never send an email out to the internet. All emails, including the NDRs, are forwarded to your destination SMTP server for delivery. In this case, when SpamFilter forwards the NDR to your mail server, your mail server in turns rejects the email with the error logged above after the phrase "The remote server said": "550 unknown user <hidden@thisdomain.com> --"

You will need to ensure that your server allows SpamFilter to relay emails to the internet, in order for them to be delivered.

Please note that SpamFilter allows you to specify a separate SMTP server to be used to deliver NDR emails via these settings in the SpamFilter.ini file:

;An alternate server for sending NDR (non-delivery) notification emails can be used. Leave the "NotificationSMTPServer" value blank to use the default destination SMTP server
NotificationSMTPServer=
NotificationSMTPServerPort=25
Roberto Franceschetti

LogSat Software

Spam Filter ISP
Back to Top
dman3883 View Drop Down
Newbie
Newbie


Joined: 09 September 2008
Status: Offline
Points: 2
Post Options Post Options   Thanks (0) Thanks(0)   Quote dman3883 Quote  Post ReplyReply Direct Link To This Post Posted: 10 September 2008 at 2:19pm
Ok I'll check it out. But why would all the other NDR's be delivered, like rejections for blacklisting, just not the NDR for an unknown user?
Back to Top
LogSat View Drop Down
Admin Group
Admin Group
Avatar

Joined: 25 January 2005
Location: United States
Status: Offline
Points: 4068
Post Options Post Options   Thanks (0) Thanks(0)   Quote LogSat Quote  Post ReplyReply Direct Link To This Post Posted: 10 September 2008 at 4:43pm
Because when SpamFilter rejects an email due to it being spam, SpamFilter, unlike many other products, is not actually sending an email back to the sender (this is a **terrible** practice, as you would be sending an email back to the sender for every spam you receive...). When SpamFilter rejects a spam email, it does so by outputting an SMTP error code during the SMTP transaction. This forces the *remote server* to send out the NDR email back to the sender, not your SpamFilter. Doing so saves a lot of resources, bandwidth, and prevents your network for being blacklisted as a source of spam yourself.

The only times SpamFilter will actually send an NDR is if it encounters problems when delivering clean emails to your server, as in when a user does not exist or when their mailbox is full for example.
Roberto Franceschetti

LogSat Software

Spam Filter ISP
Back to Top
 Post Reply Post Reply
  Share Topic   

Forum Jump Forum Permissions View Drop Down



This page was generated in 0.094 seconds.