var dict = File.ReadLines("test.txt")
.Where(line => !string.IsNullOrWhitespace(line))
.Select(line => line.Split(new char[] { '=' }, 2, 0))
.ToDictionary(parts => parts[0], parts => parts[1]);
or
enter code here
line="to=xxx@gmail.com=yyy@yahoo.co.in";
string[] tokens = line.Split(new char[] { '=' }, 2, 0);
ans:
tokens[0]=to
token[1]=xxx@gmail.com=yyy@yahoo.co.in"