Possible to customize maximum message size based on internal or external mail?

[aswinp]

Hi All, I am using the open source zimbra for my small organisation, v4.5.6_GA_1044.

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Basically I want to set the system such that:

1. For internal mail, example from xxx@internal.corp to yyy@internal.corp, the max message size is 10MB

2. But, for internal to external mail or vice versa, the max message size is 4MB

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Is this possible, has anyone done it with Zimbra?