Coupons get by email_restrictions

[DragonSoftGit]

Please help.. anyone know how to filter coupons by email restrictions .. I tryed like this but always retrive all coupons..

Dictionary<string, string> cup = new Dictionary<string, string>();
var mejl = mojkupac.email;
cup.Add("email_restrictions", "my email adres set in coupon");

var cup = await wc.Coupon.GetAll(cup);