IMAP Question

Posted on 2008-10-29
Last Modified: 2008-11-17
Greetings experts.
We are a 27 employee company.  We have outsourced our e-mails to MailTrust and are using IMAP with Outlook 2007 and Entourage 2008.  We have a full T1 connection.  I setup everyone so Outlook checks for mail every 6 minutes.  We have users with 6-7GB of emails and some of them have 4000 emails in their Inbox.

I have noticed that during the work hours our internet speed if extremely slow, b/c this IMAP process is sucking up all the bandwidth.

I was wondering if you guys knew a way to optimize or adjust certain settings in Outlook 2007 so our internet bandwidth does not get destroyed.

Any ideas out there?  Thank you very much in advance.
Question by:CompuTurk
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LVL 23

Expert Comment

ID: 22837256
I'm hoping that all those emails are in local PST files and not on the internet mail host server itself..
LVL 26

Expert Comment

ID: 22837262
Do most of these emails have big attachments or something? I have over 12000 emails in my inbox and it's about 250MB.

Do you have any kind of traffic shaping or QOS on your router? Email is something can be very low priority.

Author Comment

ID: 22837480
debuggerau, looking at the Data Files tab under Account Settings of Outlook 2007, for that mailbox, I see the following: C:\Documents and Settings\kevin\Local Settings\Application Data\Microsoft\Outlook\, but the size of it is only 45MB.  There is one other one that is xxxx0004 which is 1GB.  I have recently removed and added the IMAP connection back in there.

Will that do it?

jar3817, we recently got Gigabit cards installed on our machines and there is a gigabit switch we all connect to.  I doubt the IT consultants who installed it did any configurations on it.

What would you recommend we do on it?

By the way guys, I truly appreciate your help with this.  Thanks again.
LVL 26

Expert Comment

ID: 22837560
Are you sure it's imap traffic that is using up all your bandwidth? I have over 100 users and are using no where near 1.5Mbps to and from exchange. Granted we're just doing simple text emails, I don't know if your users are sending/receiving huge attachments or something.

Have you captured traffic with something like ethereal/wireshark to make sure it's imap that is consuming all the bandwidth?
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Author Comment

ID: 22837605
Our e-mail is servers are not hosted on our network.  It is a third-party company.  yes, we do receive a lot of attachments and send a lot of attachments.  But not all the time.  To test this problem, I turned off all the computers.  I turned on one and launched Outlook.  In Outlook IMAP settings, I checked the option where get all the full message, not just the header and I could see from Cisco traffic analyzer that the bandwidth was maxed out.

Where should I install and run Wireshark or Ethereal?  Is there any adjustments we can do on the router or the gigabit switch, maybe MTU levels or something?
LVL 23

Accepted Solution

debuggerau earned 500 total points
ID: 22837751
ok, let me explain why that test is not enough..

Your bandwidth is a spot measurement, it really depends on how long it maintains maximum usage for that matters.
But obviously, that Outlook would have appeared to work quite fast by itself...

My issue, is that if you have large amounts of emails stored in the server, it will need to walk through them all on initialization, causing a huge traffic spike.
If you set it for headers only, that spike will be reduced, but for that amount of emails, it may not matter... You would be doomed to a crawl forever..
If you just use the connection to deliver (the default delivery location) to your locally based PST when the inbox is located, it will only use the 'SMTP' for outbound, and the 'pop' side of email for inbound.
IMAP allows for directory listing functionality also, and that will be where the problem lays.

Expert Comment

ID: 22837824
At the lower right hand side bottom of the Outlook 2007, you have a dropped down arrow, click on arrow and select the option according to your need.
Following are the optios available
Download full items.
Download Headers and then full items
download Headers
On slow connections only Download Headers
Work offline

These are the some of the option through which you can save your bandwidth.
LVL 31

Expert Comment

ID: 22844917
If you're using IMAP for all this mail, you're paying for the server space already, I guess. Can't you use POP3 instead and just set clients to leave mail on the server? That should be a much faster connection...


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