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Serious bug

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tk View Drop Down
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    Posted: 28 June 2003 at 12:15am
Spamfilter accepts mail for a bogus user before verifying if that user is valid on the SMTP server. By the time it figures out that the email address is bogus it has already send an OK to the sending SMTP server and closed the connection. It then tries to return the e-mail on a new thread to the bogus return address provided by the spammer causing a bounce message to comeback. IP addresses, domain name and email addressess have been changed to protect the innocent.

06/27/03 22:58:49:560 -- (352) Connection from: 24.100.112.12 - Originating country : Canada 06/27/03 22:58:50:090 -- (352) Resolving 24.100.112.12 - CPE0040ca347bb4-CM400048344950.cpe.net.cable.rogers.com 06/27/03 22:58:50:090 -- (352) Mail from: bymsejw@yahoo.com 06/27/03 22:58:51:102 -- (352) - MAPS search done... . 06/27/03 22:58:51:102 -- (352) RCPT TO: dummyi@tdummy.com accepted 06/27/03 22:58:51:833 -- (352) EMail from bymsejw@yahoo.com to dummy@dummy.com was queued. Size: 1 KB 06/27/03 22:58:51:883 -- (338) Sending email from bymsejw@yahoo.com to dummy@dummy.com <=== New Thread =====> 06/27/03 22:58:51:943 -- (352) Disconnect 06/27/03 22:58:52:224 -- (338) EMail from: bymsejw@yahoo.com to: dummy@dummy.com was returned to sender - server error - Invalid recipient 06/27/03 22:58:53:225 -- (338) Error-email from bymsejw@yahoo.com to dummy@dummy.com was forwarded to 24.99.99.999 06/27/03 22:58:53:325 -- (338) server error - Invalid recipient
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Joined: 25 January 2005
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Post Options Post Options   Thanks (0) Thanks(0)   Quote LogSat Quote  Post ReplyReply Direct Link To This Post Posted: 28 June 2003 at 12:29am

tk,

SpamFilter is designed to send an email back to the sender if the recipient of their email is invalid, has a full mailbox, or similar. In order to avoid the bounce to bounce, did you set an Error Handler Email with a null return address like:

"System Administrator" <>

in the Customized Items tab?

Roberto F.
LogSat Software

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Post Options Post Options   Thanks (0) Thanks(0)   Quote tk Quote  Post ReplyReply Direct Link To This Post Posted: 28 June 2003 at 1:21pm

No. I just set it to <>. I still don't understand how that's going to help the situation? The sender still thinks that e-mail was delivered to a bogus address. Why doesn't SpamFiler do a verify (VRFY) against the SMTP server before accepting the e-mail?

This is a big problem for us because we get hundreds of e-mails for former employees and other e-mail addresses no longer in use and now in the possession of spammers. We could create a list of blocked to e-mail addresses but that would be a long list (or alternatively a white list of good to addressess).

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Post Options Post Options   Thanks (0) Thanks(0)   Quote LogSat Quote  Post ReplyReply Direct Link To This Post Posted: 28 June 2003 at 10:35pm

Not all smtp server will allow to verify users with the VRFY command.

If you set the return to null <>, when SpamFilter sends the bounce, it will be done so with a null return email, which should end things there. If the sender has an invalid email, nothing should come back to SpamFilter since there was a null return. Things are designed to work this way...

Roberto F.
LogSat Software 

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