Exchange using up T1

Posted on 2011-05-11
Last Modified: 2012-05-11
We send out about 1800 emails each month.  For the past 2 months it has been bogging down our network (using 99.2%) of our T1 while trying to send the emails.  We haven't experienced any issues before until the last 2 months.  Is it possbile a setting on Exchange got changed?  Our Core Processor said that if Exchange is set to send emails all at once, then this would clog up our T1 but if it was set to send emails individually, then shouldn't use up bandwidth.   Where might I find on our Exchange Server to check this?  Or is there any other solutions to this issue?

Thank you,
Sarah Folden
Question by:MWSB
    LVL 4

    Expert Comment

    I would do a couple of tests ...

    1). I would unplug the exchange server from the network and wait 10 minutes to verify that the T-1 line has cleared of congestion.  We are determining if the Exchange server is the cause or not.

    2). I would open Exchange System Manager, go to SERVER tab, find your server, open the tab and look in the QUEUES tab.  Look for lots of connections (there should only be 10 or so items in the Que).  If you have lots of items, there are multiple emails attempting to be delivered.

    if you see lots of items being or attempted to be delivered, that is a good indication that you may be being used as an open relay for email spammers (thus why you are congested).

    1800 emails a month on a T-1 line is not bad at all.  A T-1 line should be able to handle 1800 emails in a day.

    Exchange sends emails as soon as it processes them.  So if harry and sally both hit send at the same time, 2 emails would be processed.  It does not "store them up" and then release them all at one time.  So if Exchange is bogging down your T1, I would look to see what is running in the Que.

    Author Comment

    Thanks for the reply.  We definitely know it is our Exchange Server and yes when I opened up the que, there were a bunch waiting to send. Like 200 to, 185 to, 67 to etc. What I ended up doing, was Freezing them all and then Unfreezing one at a time to let them send.  This allowed some of our users to get into programs they were having issues with.  

    I do not want to have to do this every month.  What would cause them to hang in the que and what do I need to do to fix this?

    LVL 42

    Accepted Solution

    Take a look at your daily exchange logs and take a look at how large they are.  This will baseline the size of the email going in/out.

    Keep in mind a 5MB email going out to 200 users = 1GB worth of email but in your system it will show up as a single email going out.  

    Ensure that you have a size limit as it can drastically skew results (1000 text emails may equal 2MB), on the other hand 10 emails @ 5MB  = 50MB

    If youre mail server is freezing it could be someone sending an attachment to a personal distribution group and using up all of the T1 (192KB/s max.)
    LVL 76

    Expert Comment

    Check the outgoing message settings, i.e. you can limit how many simultaneous outgoing connections the server will have, there is no reason the server should try to send all 1800 emails at the same time, you can configure that at any one time, the server will only attempt to deliver 200 messages.  The other issue is how many messages can the server send over the same connection?
    I.e. instead of connecting 250 times to GMAIL's mail servers for each message, it would connect once and send 20.
    I think the default on exchange was 1000 messages per connection with 100 connections.

    You did not specify which version of exchange you have so not sure whether you are using the exchange built-in SMTP or have to rely on the IIS SMTP component.
    LVL 26

    Expert Comment

    Are you have any other disk, memory related issues @ the exchange server?
    you could run and ExBPA and check for any of the serious errors\warnings.
    LVL 29

    Assisted Solution

    by:Sudeep Sharma
    Are you sure that Exchange is the only application using all the bandwidth.

    Did you tried taking the Exchange out of the network for few minutes and monitored the network usage?

    Could be users are downloading the stuff they shouldn't like from torrent or online music. Further these days most of the illegal stuff are available via file sharing websites which works merely on http (port 80) and are hard to block unless you have content filtering firewall at the gateway doing that task for you. E.g. Rapidahre, megaupload, hotfile, fileserve, filesonic etc.

    Also have you checked if the public IP of your Exchange is acting as open relay or not.

    I hope that would help


    Author Closing Comment

    Assigned B.  Didn't get me the correct solution.  It may have something to do with the relay.  I'll have to test next month.  Please Close.

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