In your model, if you want to have e - mail validation, if user entered valid e - mail, you can use following regular expression: 

[RegularExpression("^(([a-zA-Z0-9_\\-\\.]+)@([a-zA-Z0-9_\\-\\.]+)\\.([a-zA-Z]{2,5}){1,25})+([;.](([a-zA-Z0-9_\\-\\.]+)@([a-zA-Z0-9_\\-\\.]+)\\.([a-zA-Z]{2,5}){1,25})+)*$",
            ErrorMessage = "You must enter a valid email address for send Error Mail address. Multiple mail addresses must be separated with semicolons (no spaces)!")]

One example of the model is:

public class DistributionListsEditModel
{
	[DataType(DataType.Text)]
	public String Name { get; set; }

	[DataType(DataType.EmailAddress)]
	[RegularExpression("^(([a-zA-Z0-9_\\-\\.]+)@([a-zA-Z0-9_\\-\\.]+)\\.([a-zA-Z]{2,5}){1,25})+([;|.](([a-zA-Z0-9_\\-\\.]+)@([a-zA-Z0-9_\\-\\.]+)\\.([a-zA-Z]{2,5}){1,25})+)*$",
		ErrorMessage = "You must enter a valid email address for send Success Mail address. Multiple mail addresses must be separated with semicolons (no spaces)!")]
	public String ReportSuccessToAddress { get; set; }

	[DataType(DataType.EmailAddress)]
	[RegularExpression("^(([a-zA-Z0-9_\\-\\.]+)@([a-zA-Z0-9_\\-\\.]+)\\.([a-zA-Z]{2,5}){1,25})+([;.](([a-zA-Z0-9_\\-\\.]+)@([a-zA-Z0-9_\\-\\.]+)\\.([a-zA-Z]{2,5}){1,25})+)*$",
		ErrorMessage = "You must enter a valid email address for send Error Mail address. Multiple mail addresses must be separated with semicolons (no spaces)!")]
	public String ReportErrorToAddress { get; set; }

	[DataType(DataType.EmailAddress)]
	[RegularExpression("^(([a-zA-Z0-9_\\-\\.]+)@([a-zA-Z0-9_\\-\\.]+)\\.([a-zA-Z]{2,5}){1,25})+([;.](([a-zA-Z0-9_\\-\\.]+)@([a-zA-Z0-9_\\-\\.]+)\\.([a-zA-Z]{2,5}){1,25})+)*$",
		ErrorMessage = "You must enter a valid email address for send Success CC Mail address. Multiple mail addresses must be separated with semicolons (no spaces)!")]
	public String ReportSuccessCcAddress { get; set; }

	[DataType(DataType.EmailAddress)]
	[RegularExpression("^(([a-zA-Z0-9_\\-\\.]+)@([a-zA-Z0-9_\\-\\.]+)\\.([a-zA-Z]{2,5}){1,25})+([;.](([a-zA-Z0-9_\\-\\.]+)@([a-zA-Z0-9_\\-\\.]+)\\.([a-zA-Z]{2,5}){1,25})+)*$",
		ErrorMessage = "You must enter a valid email address for send Error CC Mail address. Multiple mail addresses must be separated with semicolons (no spaces)!")]
	public String ReportErrorCcAddress { get; set; }
}