Email is a great platform for the exchange of messages, which can be plain text, rich text, or in HTML format. It is also a very popular method for transferring files between users, and that is where we, as email admins, can start to run into challenges. Using email as a file transfer mechanism places significant load on our servers. Binary files must be scanned, encoded, transferred, re-encoded, scanned, and stored as a blob in a mail database. A single PowerPoint presentation can easily take up more room than several thousand messages, which can lead to huge burdens on our email servers’ storage infrastructure. As a result, it is only good management to implement Exchange 2010 message size limits.
When you set out to implement Exchange 2010 message size limits, you first want to decide the scope of your limits. You can set limits for the entire organization, on all users with mailboxes on a specific database, or on a user-by-user basis. You can also set one limit internally and another externally. Resist the temptation to do any of these. You want to set a “one size fits all” limit. It may be tempting to allow larger message size limits when you are only dealing with internal users, but I have seen too many times where this leads to confusion, especially when a user sends a larger attachment to a mix of internal and external users, and it gets to some but not others. Or a user with a smaller limit tries to forward a message they got from another user… you can see where this can go. Stick with a single uniform email size limit if at all possible, and apply that to both incoming and outgoing messages.
Configuring Exchange 2010 message size limits
Once you have decided on a message size limit, you need to deploy this setting within your organization. You can do this easily using the Exchange Management Shell. Log onto a hub transport server and open the Exchange Management Shell. The default in Exchange 2010 is 10MB. If you want to set a 20MB limit for incoming and outgoing messages, use this command:
set-transportconfig –maxsendsize 20 MB –maxreceivesize 20 MB [enter]
Running this on a Hub Transport server will write these values to Active Directory, and apply to all Hub Transport servers in the organization. You can also run this on an Edge Transport server, but it will only apply to that specific Edge Transport Server.
Using the Exchange Management Console
You can also set limits on the connectors using the GUI, which may be preferable when working with an Edge Transport server. Open the EMC, browse to your connectors, and set a value in KB, like this:
Individual User Settings
If you must set limits on an individual, use the EMC to access the properties of their mailbox. Go to the Mail Flow Settings tab, select Message Size Restrictions, and you can set specific values for both sending and receiving messages. When you do this, you are setting a more restrictive value. You cannot use this to let a user send messages larger than the organization limits you set on the hub transport servers or a specific connector.
If you want to read more about other ways to set differing limits, you can refer to the Microsoft TechNet article at: http://technet.microsoft.com/en-us/library/bb124345.aspx, but please consider carefully before you try to set different limits on different groups. Consistency makes for a predictable and easily manageable scenario. Having different values for different users or groups will become an administrative burden. Consider alternative solutions for exchanging larger messages like SharePoint, Dropbox, or FTP.