BitServer.POP3message.isMail C# (CSharp) Method

        private bool isMail(string Message)
        {
            var space = new char[] { ' ' };
            var lines = Message.Split('\n');
            if (lines.Length > 0)
            {
                int i = isMailList(lines[0]) ? 2 : 0;
                for (i+=0; i < lines.Length; i++)
                {
                    if (lines[i].Trim() == string.Empty)
                    {
                        break;
                    }
                    else if (lines[i].Trim().ToLower().StartsWith("return-path:"))
                    {
                        retpath = lines[i].Split(space, 2)[1].Trim();
                    }
                    else if (lines[i].Trim().ToLower().StartsWith("from:"))
                    {
                        from = lines[i].Split(space, 2)[1].Trim();
                        if (string.IsNullOrEmpty(retpath))
                        {
                            retpath = from;
                        }
                    }
                    else if (lines[i].Trim().ToLower().StartsWith("to:"))
                    {
                        to = lines[i].Split(space, 2)[1].Replace(BR_SUB, BR).Trim();
                    }
                    else if (lines[i].Trim().ToLower().StartsWith("subject:"))
                    {
                        subject = lines[i].Split(space, 2)[1].TrimEnd();
                    }
                }
            }
            return (retpath.Length > 0);
        }