Not able to send email to few domains


Hi ,

I am using exchange 2010 SP1, everything was working fine until couple of days back. Suddenly, i am getting below error while sending the email to the below domains. I am using Trend Micro IMSS v7 for replying the emails. Any thoughts, why suddenly i started receiving the below message?

"Can not deliver the message you sent. Will not retry.

Sender: <user@mydomain.com>

The following addresses had delivery problems

<user@cio.gov.bh> : Reply from cio.gov.bh[89.31.193.114]:
        <<< 554 5.7.1 Message refused by DNSBL check. dul.dnsbl.borderware.com / 172.188.100.21 This is an automated message from the mail system.  This email has been rejected. The email message was detected as spam."

While 172.188.100.21 is my mailbox IP address, i am aware of the fact that this IP belongs to a public range of IP's but we have built in network with this range already so can't really do anything at the moment.

tayyabq8Asked:
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jakethecatukCommented:
you are probably on some spam blacklists

http://mxtoolbox.com/blacklists.aspx will help you work out which one
ProtechCTCommented:
Check to see if your domain has been blacklisted

http://www.mxtoolbox.com/ Is just one site you can check

When you get there click blacklist enter your external IP address, the resulting page will show you if your domain has been black listed due to spam problems, you can then request to be removed from the lists.  Make sure your network is clean.

Also check with borderware.com as they may have you on there black list.

Hope this helps. i just went throught the same problem.

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Paul CoffeyCommented:
Some people block any ip with a generic reverse lookup if this is your problem have your isp change the reverse dns entry to something specific for you.
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PapertripCommented:
Expanding on what paulc said,
[root@broken ~]# dig -x 172.188.100.21 +short
ACBC6415.ipt.aol.com.

Open in new window


Yeah that would be your problem.
PradeepCommented:
Its clearly stating that the email message was detected as spam.
Check whether your ip is in blacklist..
Also make sure about 3rd party antispam filtering applications if any.
If the recepient end is using any antispam apps like baaracuda, tell them to add you in whitelist.
PapertripCommented:
It's clearly stating that it is being rejected as spam due to a DNS blacklist entry because he is sending from an AOL dynamic IP.  Either send from a non-AOL IP, or use SMTP AUTH to connect to AOL's mail server and relay through them (if they even allow that).


Outbound Email Policy of The Spamhaus Project for this IP range:

This IP range has been identified by Spamhaus as not meeting our policy for IPs permitted to deliver unauthenticated 'direct-to-mx' email to PBL users.
http://www.spamhaus.org/pbl/query/PBL053017
Paul CoffeyCommented:
I had the same problem with users sending email via gmail through their smart phones.  At the end of it I had to stop using the entire spamhaus dbl and specify individually the ones I wanted to use and leave off the PBL.  Everything I tried on the smart phone side failed to work.
PapertripCommented:
Hey Paul,

Yeah that is the same issue, the correct way to do that is relaying through Gmail using SMTP AUTH.
tayyabq8Author Commented:
Thank you all for the comments.

FIrst of all i have checked from http://mxtoolbox.com/blacklists.aspx already and my domain is not blacklisted.

@paulc: Could you pls explain how generic reverse lookup can be blocked and what i have to ask to my ISP, because everything seems to be working fine before, this happened suddenly, before the users were able to sent email on mentioned domain.

@Papertrip: 172.188.100.21 is my internal private LAN IP, how come it is sending through aol ip?

We have IMSS thought which the emails are replayed and the mentioned domain is already added in the white list there.
PapertripCommented:
172.188.200.21 is not a private IP, it is an IP owned by AOL.

Please confirm your actual public sending IP so we can test with the correct information.

http://en.wikipedia.org/wiki/Private_network




`
tayyabq8Author Commented:
Papertrip: Am aware that 172.188.100.21 is not an private IP what i meant is am using this IP internally in my LAN network as a private range.

I guess i have found the problem, IMSS is sending emails out from aol IP rather than the actual IP.

I have checked the DNS records and IMSS setting they looks fine to me, in this case what things should i check?
PapertripCommented:
This is making less and less sense as we go.

Is AOL your ISP?  Do you have the same public and private IP space or something?

Even though you are using that AOL public address for your private space (bad), the receiving server is going to see your actual sending IP.  Your original question mentions 172.188.100.21 in the bounce message and in your comments -- is that really the IP that was in the bounce mail?

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