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Your should notify the US Postal Inspectors that the Ex Wife has made that change of address - that is a crime and they will investigate - see here: http://postalinspectors.uspis.gov/
The fact that she cahnged his mail addressalso provides a basis for him to go to court to get a TRO against her, and also will help him avoid her TRO concerning his right to visit his children.
Go for it! All the best,