Kamasutra 5.4.60

5.4.60

svabhāryāṃ vā mūḍhāṃ prayojya tayā saha viśvāsena yojayitvā tayaivākārayet/ ātmanaś ca vaicakṣaṇyaṃ prakāśayet/ sā bhāryā dūtī/ tasyās tayaivākāragrahaṇam//

(6) When a man gets his wife to gain the confidence of a woman whom he wants to enjoy, and to call on her and talk to her about the wisdom and ability of her husband, that wife is called a wife serving as a go-between. In this case the feelings of the woman with regard to the man should also be made known through the wife.