Try this:
string textWithEmails = "Christian has christian@email.com. Olof has the email olof@gmail.com. Lars has the emai britt123@oxford.co.uk.";
string filteredStr = Regex.Replace(textWithEmails, @"([a-zA-Z0-9_\-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([a-zA-Z0-9\-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})", "[EMAIL]");
Console.WriteLine(filteredStr);
The regular expression that I used is the email regex from the Regex Library of
Expresso[
^]
It is a rather complete regex, but not 100% complete. For a complete email regex, have a look here:
http://ex-parrot.com/~pdw/Mail-RFC822-Address.html[
^]