Mailbox size limits and Outlook

Hi

We have mailbox limits in our Exchange 2003 organisation set at 10MB for message sizes.

So I assume if someone tries to send a 11MB attachment, it will be bounced back by that user's Exch server.

However, if someone tries to attach a 100MB, it will still (theortically) go to Exchange and then be rejected.

Couple of questions;

a) Does the message size affect transaction log generation proportionately? I mean, will a 100MB attachment generate more transaction logs than a 1MB attachment?

b) If  a user tries to send a 100Mb attachment, more than likely their Outlook 2003/2007 will crash. Is there anyway that we can configure Outlook/ Exchange to prevent the file from even being attached if it's more than 10MB? Or do we have to wait for the message to get to Exchange (also taking up bandwidth), before Exchange rejects it?

Thanks!
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kam_ukAsked:
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hodgeyohnCommented:
a) Does the message size affect transaction log generation proportionately? I mean, will a 100MB attachment generate more transaction logs than a 1MB attachment?  

this will only effect the sender as the recipient will reject the message.  in the sent items you would still have the attachment, and it will effect the database as such.

b) If  a user tries to send a 100Mb attachment, more than likely their Outlook 2003/2007 will crash. Is there anyway that we can configure Outlook/ Exchange to prevent the file from even being attached if it's more than 10MB? Or do we have to wait for the message to get to Exchange (also taking up bandwidth), before Exchange rejects it?  

Sorry no way to protect users from themselves.

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tigermattCommented:

Hey kam,

All your points are correct. A point to note is that if someone sends a 100MB attachment through email, that 100MB attachment may still end up filling their mailbox to 200MB in capacity, since it would be in the 'Sent Items' box and there would be a duplicate of the sent message in the NDR returned into their Inbox. In your environment this probably isn't a problem, but in a few schools where I consult, their Exchange Servers often suffer greatly from this when students don't realise their message bounced, and fail to go back and cleanup the bounced messages!

a. Yes. In Exchange 2003 Transaction Logs are generated for every 5MB worth of data which passes into and out of the databases. This could be mail coming in from outside, mail being moved by a user, internal email or mail being sent by a user. In Exchange 2007, the threshold for transaction log generation was reduced to 1MB per transaction log, to make features such as CCR more attractive.

b. Unfortunately not. If a user attaches a 100MB file, when they press Send, it is likely Outlook will appear to hang, but of course it will simply be sitting there uploading the 100MB attachment to the Exchange Server. The only time Outlook is going to prevent the user sending before it has the chance to upload the attachment is when the user's mailbox is already over their 'Prevent Sending Messages at xxx KB' limit, in which case Outlook will popup a message alerting them to this. In all other cases, the messages must go to the Exchange Server, where the bounce would be generated and sent back to the user.

-Matt
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Jack_FrenchCommented:
Hello -
A) - no, only items that are written to the DB would be written in the logs. Transport would reject the message (and 100mb attachment) before it would be written to the db.

B) - check out this kb, it shows all the places you can set the message size limit
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Jack_FrenchCommented:
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nsx106052Commented:
On exchange you can set a limit.  I do do that and see if the problem goes away.
http://www.msexchange.org/tutorials/Set-Size-Limits-Messages.html

You could also write a script for Outlook to deny accepting large files.  I will have to do some more research on this.  I haven't done it in years.  

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fishadminCommented:
To my knowledge:
A) No, Exchange doesn't accept the message so the logs don't receive the attachment.  It just gets bounced.
B) I don't think you can configure outlook, but exchange should bounce it first.

Basically the header gets to Exchange and then Exchange decides what to do with it before the email is sent.  If you want to block from the outside in then your spam filter can usually be configured to block attachments of X size.
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tigermattCommented:

davidgreen, I'm afraid Exchange does receive the message. The message goes into the Exchange database since it is stored in the user's 'Sent Items' folder, and since it is written to the database, a transaction log (100MB/5MB = 20 logs, actually) is generated. Fortunately we have Single Instance Storage, so the message which bounces back and contains a copy of the original message does not generate another 100MB of data in the database, but as per the rules of SIS, it would push the user's mailbox quota up by 200MB until they clear the oversize messages out.

-tigermatt
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fishadminCommented:
That is awful.  I stand corrected and humbled :)

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