Size for group distribution email address

What is the recommended bulk email size restriction on my Exchange 2010 server, supporting 850 users with 10MB internet bandwidth ?

In Exchange storage, will the mail size is stored as 850 copies or one copy only ?

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The feature by which there is only one copy of mail is stored is known as Single Instance Storage. This does not exist in Exchange 2010. But Microsoft is saying they have compression algorithm used in Exchange 2010 which reduces storage use. You could refer the following article for more information regarding this.

Regarding email size restriction, it can be set in multiple locations. Please refer following articles for more information.

Since you have 10 MB internet bandwidth and if your users are sending unnecessary bulk mails to internet, you could reduce the default 10 MB limit. But if users are sending legitimate mails, you could review increasing your bandwidth. It would be better not to reduce default limit for Receive Connectors as it may generate NDRs for incoming mails from internet or partner organizations. If you have good bandwidth within the organization, you could increase the limit set on Transport Settings.
AXISHKAuthor Commented:
I want to restrict the size of the email, so what's the reasonable single size of a email ? We have 850 mailbox on the server.

Out of the different options mentioned in the previous post, in which option you want to restrict the mail size. Based on the location you need to set the limit.
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AXISHKAuthor Commented:
I will restrict the mail delivery size on the Distribution email address. But my question is that's the size allowed to delivery to this group email address, supposing 850 mailboxes with 10MB internet pipeline. Should I restrict the size to 100K ?

Gareth GudgerSolution ArchitectCommented:
Hey Axishk,

Just to clarify. Are you saying you have all 850 users in one distribution group and you want to limit the size of the email that can be sent to that distribution group?

If so you can do this from EMC >> Recipient Configuration >> Distribution Group. Then right click on the desired distribution group and select Properties from the context menu. Go to the Mail Flow Settings tab and double click on Message Size Restrictions. Check the box for Maximum message size, enter a value in kilobytes and click Ok twice.

100KB should allow emails to come in. Especially plain text or rich text. But it will block most any email with an attachment. Any email with a picture will have a hard time getting through at that limitation as well.
AXISHKAuthor Commented:
my estimation of 100K is based on a worst case where 850 users downloading the email at the same time,

850 x 100K = 85MB (85MB * 8 --> 680Mb  --> 680Mb / 10Mbps  --> 68s). Hence, my internet pipe will not overload with more than 2 min.

Am I correct ?
Gareth GudgerSolution ArchitectCommented:
Hence, my internet pipe will not overload with more than 2 min.

If someone external sends a message to a distribution group then only one copy of that message is sent to Exchange over your internet connection. Once Exchange receives it, it then enumerates the group memberships during the transport process and delivers that message to those 850 users as separate messages.

This sounds like an "Everyone" or "All Company" distribution group. I typically don't allow external (anonymous) users the ability to send to a distribution group like this or of that size.

What about locking it down so only internal users can send to this distribution list?

Another option might be to set it up for delegation. That way any message sent to that distribution list has to be moderated by an individual for approval. You can make exceptions to who need moderation as well.

If you do need that distribution list wide open to internal and anonymous users then as you mentioned any user device will download it. Whether via Outlook Anywhere, or, ActiveSync. Those users could also have multiple devices (phone, tablet, laptop).

You may wish to look at the Exchange Sizing Calculator as well.

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AXISHKAuthor Commented:
Sorry, can't fully understand your explanation. Does my assumption estimate above correct ? Tks
Gareth GudgerSolution ArchitectCommented:
The math looks good to me.

But this also assumes that everyone is downloading the message at exactly the same time.

The math also assumes that your users are only receiving email on one device.
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