using System;
using System.Text.RegularExpressions;
 
public class Test
{
	public static void Main()
	{
		var email = "2011,01,10   a,john.doe@gimail.com";
        string result;
        string pattern = "gimail\\.";
        string replacment = "gmail.";
 
        Regex rgx = new Regex(pattern);
 
        email= rgx.Replace(email, replacment);
 
        pattern = @"(?<=\p{L}),";
        replacment = ".";
 
        rgx = new Regex(pattern);
        result = rgx.Replace(email, replacment);
        Console.WriteLine(result);
	}
}

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