Used the above code in MVC5 project and it works completely fine with the validation error. Just try this code:
[Required]
[Display(Name = "Email")]
[EmailAddress]
[RegularExpression(@"^([A-Za-z0-9][^'!&\\#*$%^?<>()+=:;`~\[\]{}|/,?€@ ][a-zA-z0-
9-._][^!&\\#*$%^?<>()+=:;`~\[\]{}|/,?€@ ]*\@[a-zA-Z0-9][^!&@\\#*$%^?<>
()+=':;~`.\[\]{}|/,?€ ]*\.[a-zA-Z]{2,6})$", ErrorMessage = "Please enter a
valid Email")]
public string ReceiverMail { get; set; }