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!!!URGENT - SMTP Service clogging up bandwidth after someone emails to distribution list!!!

I have a customer with Exchange 2003 on Server 2003 that when a particular user sends an email out to some of his personal distribution lists, it brings the Internet connection (DSL) to it's knees.  I notice there are about 250 individual queues within ESM.  Each on has one email in it.  They never seem to deliver.  It happened yesterday and I created a new SMTP Virtual server and pointed the connector to is and that seems to calm it down.  The user did the same thing again today and it happened again. Yesterday I turned off NDRs on the server and change the retries so something less than 60 minutes.  I have logging turned on on the MSExchangeTransport and I am getting a bunch of the following in the app logs.  When I stop the SMTP Virtual server within ESM, the internet connection comes back.

CAN ANYONE TELL ME WHAT IS GOING ON?

Event Type:      Warning
Event Source:      MSExchangeTransport
Event Category:      Connection Manager
Event ID:      4000
Date:            4/5/2006
Time:            9:47:48 AM
User:            N/A
Computer:      SERVER02
Description:
Message delivery to the remote domain 'liberty-development.com' failed for the following reason: Unable to bind to the destination server in DNS.


Event Type:      Warning
Event Source:      MSExchangeTransport
Event Category:      Connection Manager
Event ID:      4006
Date:            4/5/2006
Time:            9:47:48 AM
User:            N/A
Computer:      SERVER02
Description:
Message delivery to the host '204.200.209.41' failed while delivering to the remote domain  'orgholdings.com' for the following reason: An SMTP protocol error occurred.

Event Type:      Warning
Event Source:      MSExchangeTransport
Event Category:      Connection Manager
Event ID:      4006
Date:            4/5/2006
Time:            9:47:51 AM
User:            N/A
Computer:      SERVER02
Description:
Message delivery to the host '216.31.169.57' failed while delivering to the remote domain  'newplan.com' for the following reason: The remote server did not respond to a connection attempt.
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ClearBlueTechnologies
Asked:
ClearBlueTechnologies
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3 Solutions
 
ClearBlueTechnologiesAuthor Commented:
Here is another common one during this issue.


Event Type:      Warning
Event Source:      MSExchangeTransport
Event Category:      Connection Manager
Event ID:      4006
Date:            4/5/2006
Time:            10:00:46 AM
User:            N/A
Computer:      SERVER02
Description:
Message delivery to the host '65.214.51.132' failed while delivering to the remote domain  'larrysteinrealty.com' for the following reason: The connection was dropped by the remote host.

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f_umarCommented:
u can set limit the number of conncetions to something between 20 to 50 in smtp virtual server.
or u configure a smtp connector and use your isp smtp as a smart host.

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ECNSSMTCommented:
the last two specifies connectivity issues. and I'm kinda wondering if the 1st two vaguely points to that also.  What is the upload speed on the DSL?  http://www.dslreports.com/

I am wondering if this mass mailing is overwelming the DSL connection during the particular time of day that this person is doing this.  Everything else just may be the fall out.  I assume that there are other users utilizing the internet for web surfing and email.

If you want to test this hypothosis, maybe have this user send out his mass mailing, very early or very late in the day to avoid the normal traffic.

Regrards,
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SembeeCommented:
I would look at your DNS configuration. The default configuration that most sites are using isn't optimised for dealing with a large number of queries that a distribution list would generate.

Ensure that the Exchange server is using the domain controllers ONLY for DNS, and that there are no external DNS servers configured anywhere in the network settings or in the Exchange application itself.
On the domain controllers, configure the DNS server to use forwarders and then enter your ISPs DNS servers in as forwarders. The default configuration uses the internet root servers, which are further away. In many cases the ISPs DNS servers are one or two hops away and are able to respond much more quickly.
If this user regularly sends to the distribution list, then the DNS information will be cached which should improve performance.

However... if this is a regular thing - once or twice a day, then you might want to consider spinning the list out to a dedicated product. Lyris has a free version that may well be enough for this user. It will manage the sending of this much better than Exchange will, and can also manage the bounce backs that are generated.

Finally, another option would be to send all your email through your ISPs SMTP server. You may well have to do this with some of your email anyway as you are on a DSL Connection.

Simon.
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ClearBlueTechnologiesAuthor Commented:
When the connection is not locked up because of the SMTP service, the download:4Mb, upload:300Kb.  When the SMTP service locks it up, the download:700Kb, upload:20Kb.

If I set my connections to say 50 on the SMTP virtual server, that effectively means that is only going to try to send 50 emails (or establish 50 connections) at a time?

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ClearBlueTechnologiesAuthor Commented:
I am getting a bunch of NDR reports in a mailbox that I have setup for that purpose.  They have a variety of errors but if it is a DNS issue, could it be that these messages are timing out and that is why I the NDR?  I also notice that all the distribution list appears to have a bunch of invalid email addresses...could that cause I problem too?
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SembeeCommented:
If there are invalid addresses then that will cause problems. Sounds like this distribution list isn't very clean.
Email isn't supposed to timeout for 48 hours, so if the messages are bouncing back immediately, then I would suspect that there is a problem with the DNS for that domain. Confirm it with the tools at dnsstuff.com

If the user is regularly sending out emails to this list and hasn't cleaned the list recently, then something needs to be said, or restrictions placed on the user until it is cleaned up as it is having an impact on the business.

Simon.
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ClearBlueTechnologiesAuthor Commented:
I will check into the DL issue.  I have a question about DNS.  In this environment, I have two servers, both domain controllers. One is 2000 (A) on is 2003 (B).  I have them both running DNS. A points to itself as primary and B as secondary.  B points itself as primary and B as secondary.  B has Exchange on it.  Is this a good setup or should it be different?  DNS is redundant through AD correct?
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SembeeCommented:
That DNS configuration is fine.
The key point is what you have done with the DNS server on the domain controllers themselves - whether you have configured the forwarders or not.

Simon.
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ClearBlueTechnologiesAuthor Commented:
I setup the forwarders and things seem to be better but it still chokes the Internet connection when he sends it.  We tried pairing the list down to about 20 recepients and still made a noticable impact on the internet connection.  He is sending a 1MB attachment to everyone in the DL.  Is there a way Exchange can stagger the sending of these emails so that is doesn't choke the connection?
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SembeeCommented:
Setup another SMTP Connector and restrict the size of the messages. You can configure the SMTP Connector to send anything over a certain size at a later date.

Simon.
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ClearBlueTechnologiesAuthor Commented:
So if I leave the first connector there and create another one for large messages.  How does it figure out which connector to use when the Allowed Sizes field says "Only messages less than xxx (Kb)"?  Would I have to specify a size on one and not on the new one, then it would use it?
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ClearBlueTechnologiesAuthor Commented:
Is there a way to say that if the email is xxx Kb in size and sent to 50 people...send it after a certain time?  Or simpler, is there a way to send emails to DLs of a certain size after a certain time?
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ClearBlueTechnologiesAuthor Commented:
Tell me if you think this would work:

I could setup one connector (A) to run always and send low and medium priority emails under 850K during normal working hours and anything over send it after hours.  This would handle most emails throughout the day and any large ones to DLs (the current cause of my problem) after hours.  The only problem this would create is if someone needs to send one email to someone during the day that is larger than 850K.  To solve that I would create another connector (B) to handle high priority emails, run always.  Then if someone wanted to send a one-off email with a large attachment, the just have to assign it a high priority.  I plan on testing this but wanted to get some thoughts.

Thanks,
Mike
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SembeeCommented:
If you already have an SMTP Connector, then you don't need to create an additional one.
In the connector under Delivery Options there is a setting for messages over a certain size - which you can set to run on a different schedule.

Otherwise the plan that you have outlined would work - as long as the person sending out the distribution list email message doesn't abuse the fact and bypass your restriction.

Simon.
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f_umarCommented:
use the smtp connector schedule and reduce the expiration time of a message also you can extend the retry interval to recover bandwidth
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ClearBlueTechnologiesAuthor Commented:
Thank you for all of your help!  I think the problem was a combination of a mass email with a large attachment (1+Mb) to a dirty DL and the Exchange server using Root DNS servers instead of closer ISP DNS servers.  I appreciate all of the tweaks that have been mentioned.

If anyone knows how to schedule emails sent to distribution lists without 3rd party (unless it is free or cheap), I would love to hear about it.

Thanks!
Mike
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