首先在BOS设计器上找到发送邮件这个元数据，然后拓展，挂上二开表单插件。表单插件示例代码如下：

public class SendMailDefault : AbstractDynamicFormPlugIn
    {
        private string FMailAddress = "FMailAddress";
        private const string FSendee = "FSendee";
        private const string FUser = "FUser";
        private const string FToAddress = "FToAddress";
        private const string FSendeeKey = "FSendeeKey";

        public override void AfterBindData(EventArgs e)
        {
            base.AfterBindData(e);
            SetCustomer();
        }
        private void SetCustomer()
        {
            BusinessInfo info = this.View.OpenParameter.FormMetaData.BusinessInfo;
            Entity entity = info.GetEntity(FMailAddress);
            int count = this.View.Model.GetEntryRowCount(FMailAddress) - 1;
            this.Model.InsertEntryRow(FMailAddress, count);
            DynamicObject objRow = this.Model.GetEntityDataObject(entity, count);
            info.GetField(FSendee).DynamicProperty.SetValue(objRow, this.View.Context.UserName);
            info.GetField(FSendeeKey).DynamicProperty.SetValue(objRow, this.View.Context.UserId);
            info.GetField(FToAddress).DynamicProperty.SetValue(objRow, this.View.Context.UserEmail);
            this.View.StyleManager.SetEnabled(FUser, objRow, "LockFieldService", true);
            this.View.StyleManager.SetEnabled(FToAddress, objRow, "LockFieldService", false);
            this.View.UpdateView(FMailAddress);
        }
    }