A first electronic message collector collects electronic messages travelling on a first network and stores the electronic messages in a first storage. A second electronic message collector collects electronic messages travelling on a second network and stores the electronic messages in a second storage. An electronic message associator retains a mapping table in which the correlation, or similar, between electronic messages travelling from the first network to a gateway device and electronic messages travelling from the gateway device the second network are defined. The electronic message associator references the mapping table and associates the electronic messages stored in the second storage with the electronic messages stored in the first storage. From the result of the above-mentioned association, a status analyzer determines whether or not receipt of electronic message between the first network and the second network is accomplished normally.
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