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Do Attachments create multiple duplicates when sent to multiple users?

Last Modified: 2013-11-14
Do Attachments create multiple duplicates when sent to multiple users. In other words when 1 or more file attachments are sent to multiple users internally on the same domain are duplicates created essentially multiplying the amount of data taking up space too? I am trying to get users internally to stop doing this and use our shared network drives to help conserve a TON of disk space. If I am assuming wrong at least I can stop the insanity of the effort. If it holds true I may just block users from having the capability of attaching files and sending to users internally...
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AFAIK, when this happens, one instance of the real "attachment" is created in the database and then the "attachments" in the emails to remaining users are just pointers to the original "attachment". I'm sure that someone else can explain this better, but that's how i understand it.
tigermattSite Reliability Engineer
Most Valuable Expert 2011

All flavours of Exchange from at least Exchange 2000, but possibly including Exchange 5.5, use a feature known as Single Instance Storage. This feature essentially means the Exchange databases are a complex relational database, whereby all data is stored just once. A record is then added to "map" each email message to one or more internal recipients.

So, for mail sent out to many internal users, the message will only be stored in the Exchange database once. However, although the data is only stored once, every users' mailbox quota restriction will be charged the full size of the message.

The only time you will have problems is when the large messages are forwarded or replied to, and the large data file or piece of data is included in the forward/reply message. Since this is a separate message in its own right, it will use up additional space in the Exchange database.



Thanks Everyone! I suspected it might work that way. One last question for now. Is there a way to monitor email content at the server? Currently I have created additional profiles in my outlook of every user and look that way or I just log into there account on the Terminal Server. Both methods have its inconveniences. Any sugestions?
Site Reliability Engineer
Most Valuable Expert 2011
This one is on us!
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Just to throw this into the ring, there are services out there that archive all mail and make it searchable for compliance reasons (SEC, FINRA etc). They do this by utilizing Exchanges journaling feature. As tigermatt points out, check the legal ramifications of doing this before you implement. We use an archiving solution from www.smarsh.com to exactly this for SEC compliance. May not be exactly what you are wanting to do, but I thought i'd throw it out there.


Thanks Again Everyone! Our employee handbook does state that email and computer usage may be monitored. Thanks for the heads up though!
tigermattSite Reliability Engineer
Most Valuable Expert 2011

In that case, it shouldn't be a problem.

Are you aware of the procedure to close a question and assign the points to expert comment(s)?


I was actually just going through the process for my first time...Thanks!

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