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Are we blocked by the remote server?

Posted on 2004-09-28
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Last Modified: 2012-06-27
This is the search result of our IP address on www.openrbl.org:
Results: Positive=1, Negative=28, Timeouts=1 (2004-09-28 13:50:22 UTC)
@ISP/blackholes.us: 65.211/16: 553 ISP MCI - http://hatcheck.org/google?mci; http://hatcheck.org/sbl?mci; ISP UU - http://hatcheck.org/google?uu; http://hatcheck.org/sbl?uu [Blockparade]
Negative 28: @COUNTRY @DYNAMIC @SPAM AHBL AUDNSBL BOGONS BOPM CBL DRBL DSBL FIVETEN INTERSIL JIPPGMA LNSG NJABL NOMORE ORDB PSBL RFC_IPWH SBL SORBS SPAMBAG SPAMCOP SPAMRBL SPAMSITE SPEWS UCEPROT WPBL
Timeouts 1: BLARS

NDR received by the user:
 'recipient@@companyA.com' on 9/28/2004 6:31 AM
            There was a SMTP communication problem with the recipient's email server.  Please contact your system administrator.
            <OurExchangeServer.OurInternalDomain.com #5.5.0 smtp;550 <recipient@companyA.com>, Recipient unknown>

Result of telnet test on remote server:

250 OK
250 2.1.0 ....Sender OK
250 2.1.5
354 Start mail input; end with <CRLF>.<CRLF>
250 2.6.0 <CAPWEBYQYx3G5aYY61L000001fe@> Queued mail for delivery
221 2.0.0 closing transmission channel

Does the code 2.6.0 indicate us being blocked by this server?  Thank you.  




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Question by:altonyoung
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by:scampgb
ID: 12170398
Hi altonyoung,

2.6.0 is a perfectly normal message, in this case it's accepted it.
Anything starting "2" is an OK/informational message.

The message you got back seems to indicate that the address you sent it to is incorrect.  If this is happening with just one receipient, I suggest that you check the email address with them.
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by:altonyoung
ID: 12170592
Thanks for the reply.  

I thought it was an incorrect email address too when I first look at this NDR.  However, when I try the email adrres using telnet, I got a 2.1.5 response from the remote server which means destination mailbox address valid.  

Is there a way to find out if either our domain or ip address is blocked by the remote smtp server using telnet?  

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Expert Comment

by:scampgb
ID: 12170952
altonyoung,
If you've tried the telnet test, you've pretty much ruled out it being something to do with your Exchange setup or SMTP.

It's possible that their mail server is silently deleting the email, or failing to deliver it for some other reason.

Try doing an RBL check at http://rbls.org/ and let us know if any come back positive.

Your best course of action is to contact the system administrators of the recipient domain and explain the problem you're having sending emails to them.
They should be able to explain what's going on - or it might point out to them that they've got a problem with their email system :-)

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Author Comment

by:altonyoung
ID: 12171318
I was hoping there were some codes from the telnet session to indicate wether there's a block on us by the remote server.

A check of our IP on rbls.org returns all OKs except the three listed below with Timeout.  

Name URL RBL-base result comments
bl.deadbeef.com http://spam.deadbeef.com/bl/ bl.deadbeef.com Timeout  
block.blars.org http://block.blars.org block.blars.org Timeout  
rbl.spam.org.tr http://rbl.spam.org.tr rbl.spam.org.tr Timeout
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scampgb earned 250 total points
ID: 12171968
altonyoung,
I wouldn't worry about the timeout ones - they'll not be causing you any trouble.

The "telnet" codes are actually the SMTP response codes.  What they're saying is that the remote system has very happily accepted the email from you.
Unfortunately it's not telling you what it's done with it once it's got it.

The only way you can really find that out is by asking the sysadmins for the domain what's happening.

From time-to-time I get asked why emails that are being sent to a domain I manage isn't arriving with the receipient.  In all cases I've been able to explain why our system thought it was spam and we were able to deal with it pretty quickly and easily.

Most system administrators are friendly enough people - so if you contact them and explain what the problem is, I'm sure they'll be able to help you.
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by:scampgb
ID: 12177752
Glad I could help :-)
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