In my opinion, you're correct, but within the context of the common practice of a particular organization, certain conventions may become sacred. If, as you say, there's nothing special about this particular "ordinary resolution," or about "ordinary resolutions" in general, it's hard to justify the caps - especially if it's a "common business letter" to someone outside the organization. Do you have access to records of other similar communications to see what is common practice for your organization?
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