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Some clients cannot do not receve email from us

Posted on 2006-05-16
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Last Modified: 2010-03-19
Hi

sbs 2003 + exchnge + 10 users

We have a strange problem.

There are some customers who never can get emails from us but we can get emails from them.
These customers have their own servers. They all say that everything is OK with them server and we should look what is wrong in our server.

Since I am new in the job, I cannot tell when and where it started to happen

I don't know where to start looking.

Please help
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Question by:zolpo
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by:jhance
jhance earned 400 total points
ID: 16693475
Are any of these customers using DNSBLs to protect their servers from SPAM?  Your IP may be blacklisted at one or more places.  Check it out at:

http://openrbl.org/
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by:CKWT
CKWT earned 400 total points
ID: 16693649
Right!, Blacklists or easy to get on, from one of you computers been infected in the past you would most likely get pretty quick on http://cbl.abuseat.org/ and that would be a reason why you dont have both ways email. stuff like that u know...

also... another reason is your DNS server is missing important ANTISPAM measures, like SPF and PTR records, also DomainKeys are getting popular, go into www.dnsreport.com and www.dnsstuff.com to find more information about your servers... probably you'll find a hole... you could probably be dealing with a Greylisting server, wich delays emails and notify your server of failure expecting that a legitimate email server will attempt to deliver and a SPAM server will receive the error and dont try that address again... It's a controversial measure but some people uses it.


Hope to help


CKWT

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by:mikeleebrla
mikeleebrla earned 800 total points
ID: 16693931
in addition to the black lists that the others mentioned,,, it is also possible that their spam filter blocked the email for any number of reasons (keyword checking,  bayesian filter, etc etc).  All you need to do is to tell them to add your domain to their 'whitelist' on their spam filter and then their spam filter will allow the email through regardless of it is on any blacklist or contains keywords that they block (assuming THEIR filter is configured correctly)

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Author Comment

by:zolpo
ID: 16694521
Thank you all for fast response.

I check our domain/ip in many black list providers and thanks god we are not spammers!

According to your advise I will talk with their admins for help.

But they already said that everything is OK within them system. So is there a place in our local system i should look for?
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by:rliptrot
rliptrot earned 400 total points
ID: 16698027
Get them to send you an email and then reply to it, if it comes to you but you cant send it, check the queues in exchange system manager you should see the message has been sent from your server.  If it cant go you will get an idea as to why.  Once its been sent, its no longer your servers problem, it must be the other end.  Had this happen a number of times and it was always the other end, but prove its not yours first, thats the nicest way to get someone to check their servers.

Also try an NSlookup from your server to the recipients mail server addresses to check its not DNS.

Open a command prompt -
type - nslookup (enter)
type - set type=mx (enter)
type - (name of recipient domain i.e. bt.com) (enter)
Once your done type exit

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mikeleebrla earned 800 total points
ID: 16699543
>>But they already said that everything is OK within them system.
you must be new to IT,,,, b/c that is what EVERY other person will say whenever something doesn't work properly.... its simply passing the buck.  Have they checked their SPAM logs to see if their filter has blocked anything from your domain???????????  that would be the first and most basic step to take.  If they haven't done that yet, they are simply lazy and passing the buck.
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Author Comment

by:zolpo
ID: 16762271
mikeleebrla you were right. They pass me the buck. After some talking they "found" the problem and fix it.


Cheers.
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Expert Comment

by:jhance
ID: 16762343
mikeleebrla,

Where are you finding IT types that pass the buck?  I've simply NEVER seen such a thing happen!!  ;-)
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