Setting Message Size Limits

There are two related message size limit settings. The Maximum message size is a preferred limit for the server. If a mail client sends a message that exceeds the limit, the message is still processed as long as it does not exceed the Maximum session size. The Maximum session size is an absolute. A connection is automatically closed if a message reaches this limit.

To set message size limits

Select the Messages property sheet, and then select Limit Messages.
In the Maximum message size box, type a value for the maximum size of a message, in kilobytes (KB). The default is 2048 KB. The minimum value is 1KB.
In the Maximum session size box, type a value to indicate the maximum size (KB) a message can be before the socket connection closes. This number will always be larger than the maximum message size and should be set carefully, because the connecting message transfer agent (MTA) is likely to resubmit the message repeatedly. The default size is 10240 KB. The minimum value is equal to the maximum message size.