You could install a network analyser such as ethereal (http://www.ethereal.com/)
Sembee also has a lot of very good guides on his website for exchange - http://www.amset.info/exch
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Exchange 2007 Spamming
We are having major problems sending email from our Exchange 2007 Server. Our server is appearing on blacklists and our outbound email is being refused. Upon inspection of the Outbound SMTP Queue, I have found literally hundreds of outbound emails, all have "From: <>" and "To:" random email domains. Its clear to me that something is using our Exchange server to send spam, most likely an internal MAPI client, however I am unsure/unable to locate the source of the problem.
Our setup is Exchange 2007 server which also is running Trendmicro Scanmail 8. The exchange server is behind a firewall and has a public IP nat'd to it on port 25. All outbound port 25 traffic is blocked expect from the Exchange IP.
This is a major problem and is effecting our business, therefore I am awarding 500 points to whoever can help me resolve this issue quickly...
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Answers
I would check to make sure you are rejecting amil to unknown users. See sembees article at http://www.amset.info/exch
You can send me a test email at test@cdlive.co.uk (post here when you have sent it) and I can see if you are on any other RBLs or there are any other problems with your mail configuration.
Thanks for the posts. I will look into these suggestions...
A specific problem I face is sending email to hotmail.com. I get the following message:
bay0-mc7-f7.bay0.hotmail.c
I havent been able to figure out how Hotmail block email and how to get us off there list.... Obviously I need to resolve the spamming issue first to prevent us from being put back on....
Another issue I am facing is most of the information I can find about securing exchange is all based on the 2003 version.... such as Sembee's pages provided above. Its difficult to find feature for feature setting in 2007. Can anyone help me with specific settings in exchange 2007? I.E. how to ensure internal email senders are authenicated etc?
I expect Sembee will post in here when he comes online. I would leave it 12 hours or so and if he does not post you can send him an email on his website.
> Received: from mail.biosme.com (unknown [83.111.160.230])
It looks like you dont have a PTR record for your IP address. You should contact your ISP and ask then to add a PTR record for 83.111.160.230 pointing to mail.biosme.com.
The only RBL I found was the UCEPROTECT one you mentioned. You say that there is no alternative ISP for you to use.
There is a way around this. You could reant a server from a hosting company and have it configured to only accept mail from your IP address and for that IP address to be trusted. You could then configure your exchange to send all outgoing mail to that server as a 'smart host'. It will then be the IP address of the rented server which matters in RBL terms so you will bypass the problem.
Hmmm.... Strange this is when I look at our domain on www.dnsreport.com it show that we have a PTR (reverse DNS entry)?? Whats up with that?
I have checked with the ISP, they have confirmed that our PTR record is inplace as follows:
160.184.111.83.in-addr.arp
DNSReport also backs up this statement.... Strange that our domain is showing up as "mail.biosme.com (unknown [83.111.160.230])". Any ideas on this?
It could indeed be that our email is being blocked due to reverse-dns lookup failure...
Ok yes.. you are absolutely right!!
The reverse DNS IP is not actually our email server.... damn how did I miss that? Just shows a second pair of eyes really helps at times.
I will now request the ISP to correct the PTR record, probably take 24 hours and I will update. Thanks for the assistance....!
Also, it seems that by disabling sending of NDR to outside, has stopped the emails building up in my outbound queue. Perhaps someone was hamering our smtp with fake domains, and our server couldnt send out the NDR's??? not sure really...
It may be related to my 2nd post I made about making sure exchange is configured to reject mail to non existing users. If you dont then you end up sending out non delivery reports to the (faked) senders email address. This in itself can get you on a RBL (http://www.backscatterer.
The messages that you are seeing in the queues are NDRs. It looks like you are facing NDR spam. Recipient filtering is available on Exchange 2007, I haven't written the article on it yet though. It is in the list of things to do.
Are you running a single server? If so then you will need to install the antispam agents first.
In powershell, change to the following directory (presuming default locations)
C:\Program Files\Microsoft\Exchange Server\Scripts
Then use tab to select install-AntispamAgents.ps1
Run that and restart Exchange 2007 EMC.
Then go to Organisation Configuration, Hub Transport and select the Anti-spam option.
Disable every option (as they are enabled by default) except for recipient filtering. Go in to the properties of recipient filtering and enable the option "Block messages sent to recipients not in the global address list" on the Blocked Recipients list.
Apply/OK out.
To get the change to take, restart the Microsoft Exchange Transport Service.
No need to enable tarpit, as that is enabled by default anyway.
To clean the queues, I don't have a good method yet (again because I haven't had time to sit and work one out) so the quick and dirty method will have to do.
In Server configuration, right click on the Server and choose properties. Click on the tab limits. Make a note of the defaults and then change each timeout to 1 minutes. Do NOT change the retry setting unless prompted to. Again apply/OK out and restart the Exchange Transport Service.
That will flush out the queues.
I would suggest that you change the NDR setting back to the default.
Simon.
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If your question has been answered, please remember to accept the answer and close the question.
HI Sembee
Well i am facing the same problem of messages in queue viewer from unwanted domains ,i think they are junk or may be spam and also it creates a dns connecters and always retry and rety i would like to now is it coming from some internal machines or are the spammers are hitting my exchange 2007 server or what is the exact issue and whats the solution for it.Kindly help me
hiyusuf - this is an old question. Unlike a forum it is not possible to "bump" questions back up the list. The only people who will see your post are those that have already participated. Instead you should post your question as a new question in the Exchange Server Zone which will allow other experts the chance to see the question and respond.
Simon
Exchange Server Zone Advisor.
Sembee,
I have tried your solutions, but for some strange reason "anti-spam" doenst block anything.
After installing the script i searched the eventlogs and got this error:
Anti-spam agents are enabled, but the list of internal SMTP servers is empty. If there are any MTAs between this server and the Internet, populate this list by using the Set-TransportConfig cmdlet in the Exchange Management Shell.
But there is no other mailservers in this domain...
so i gave this commmand: set-transportconfig -internalsmtpservers 192.168.10.100
that is the ip of my exchange server.
But still it wont work...
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by: The_R0CKPosted on 2007-10-18 at 00:59:52ID: 20099277
Also I have actually assumed that our server is appearing on Blacklists. Upon further inspection I have actually found that we only appear on one: dnsbl-3.uceprotect.net LISTED!. However this site states that it is our ISP which is listed and not our IP directly. Unfortunately in our area we only have one ISP! therefore I do not have the luxary of choice....