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Customer is getting errors e-mailing our domain and it seems to bypass spam filter

Slagwag
Slagwag asked
on
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Last Modified: 2012-08-13
We have an Exchange 2010 environment utilizing Postini for incoming e-mail. Our mail server is configured to only allow incoming e-mail from Postini so it has to get filtered rather then hitting our server directly. However one customer sending us e-mail cannot get through and gets the following e-mail back:

From: MAILER-DAEMON@messagelabs.com [mailto:MAILER-DAEMON@messagelabs.com]
Sent: Friday, February 03, 2012 12:16 PM
To: Customer Name
Subject: failure notice

This is the mail delivery agent at messagelabs.com.
I was not able to deliver your message to the following addresses.

<ouruser@company.com>:
Connected to 11.51.11.111 but sender was rejected.
Remote host said: 530 5.7.1 Client was not authenticated

Is messagelabs spam filtering somehow sending to us directly?
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Alan HardistyCo-Owner
CERTIFIED EXPERT
Top Expert 2011

Commented:
Are they sending to a distribution group or a regular user (not sure if MessageLabs can handle DGs)?

Author

Commented:
They are sending it to a user directly. Multiple users. And they are using MessageLabs - i assume from that error. We use postini.
Alan HardistyCo-Owner
CERTIFIED EXPERT
Top Expert 2011

Commented:
Then I would ask your customer to talk to Messagelabs as this is a problem between them and your customer and nothing to do with your filtering / server.

Author

Commented:
Their IT is blaming us. I am trying to do whatever I can to either fix it or prove I cannot fix it. The one thing to note that isn't clear above:
<ouruser@company.com>:
Connected to 11.51.11.111 but sender was rejected.
Remote host said: 530 5.7.1 Client was not authenticated

The 11.51.11.111 represents the IP address of our mail server. Therefore when they send an e-mail to us and MessageLabs is handling the mail, it ends up sending it to our Mail Server directly. However, our MX records are pointing to Google's postini servers. I am not sure why it is attempting to connect to our server directly.. this is strange and we block all IP's that are not Google's.
Alan HardistyCo-Owner
CERTIFIED EXPERT
Top Expert 2011

Commented:
If they are sending mail direct to your server - that is their bad configuration causing the problem (well MessageLabs) if they send mail out via them.

Ask them to call Messagelabs and explain to them that they need to use your MX records to deliver mail to your domain and not cached IP Addresses.  That way, Messagelabs can send to Postini and Postini can send direct to your server.

If anyone other than Postini sends mail direct to your server it will get rejected, which is the expected behaviour, so why is that your problem exactly???????????????????????????
Alan HardistyCo-Owner
CERTIFIED EXPERT
Top Expert 2011

Commented:
When did you implement Postini filtering?  If within the past 24-48 hours - then that would explain things, but if ages ago, then Messagelabs are at fault.

Author

Commented:
I agree with you completely. It makes sense though if they somehow are using a cached IP. I implemented Postini in early 2010 though so it has been a long time. I have contacted their support to inform them of the issue.
Alan HardistyCo-Owner
CERTIFIED EXPERT
Top Expert 2011

Commented:
2010!  Well that should have been enough time for Messagelabs to pick up the changes (or so you would have thought) :)

The problem is definitely not at your end.
Commented:
This one is on us!
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Author

Commented:
Turns out after working with MessageLabs that they had a record pending deletion for our domain. All e-mail routing to it was being delivered unsuccessfully. As soon as they deleted it completely it worked.

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