Validating E-Mails & Phone Number

Introduction

Have ever had a field on a form for a users E-Mail address or phone number and the user put garbage values in?

I've written several programs that send E-Mails and Faxes using the information provided by user input. After spending 2 days once fixing blatant typos ie Someuser At Company dot Com, I decided to write a validation routine.

They don't stop all errors, but they do reduce user accidents.

BOOL ValidateEMail(CString Address)
{
	BOOL	RtnVal = TRUE;
//	Address = "A@b.c";    // Valid
//	Address = "A@b.cnet"; // Invalid
//	Address = "A@b.c_";   // Invalid
//	Address = "A@bcnn";   // Invalid
//	Address = "Ab.cnn";   // Invalid
//	Address = "A@bc";     // Invalid
//	Address = "A@bat@.cnn";  // Invalid
//	Address = "A@bat/.com";  // Invalid

	if(Address.GetLength() < 5)
	{
		// Too short
		RtnVal = FALSE;
	}
	else if(Address.Find("@") == -1)		// Has at least 1 @
	{
		RtnVal = FALSE;
	}
	else if(Address.Find(".") == -1)		// Has a Period
	{
		RtnVal = FALSE;
	}
	else if(Address.GetLength() - Address.ReverseFind('.') > 4)		// no more than 3 characters after the final period (reverse find is 0 based not 1 based)
	{
		RtnVal = FALSE;
	}
	else if(Address.ReverseFind('_') > Address.ReverseFind('@'))	// an underscore after the @
	{
		RtnVal = FALSE;
	}
	else
	{
		// only 1 @
		int		FindPos;
		FindPos = Address.Find("@");
		FindPos = Address.Find("@", FindPos+1);
		if(FindPos != -1)
		{
			RtnVal = FALSE;
		}

		// allowed characters 0-9 A-Z _.@-
		int		Pos;
		int		NumChars;

		NumChars = Address.GetLength();
		Address.MakeUpper();

		for(Pos = 0; Pos < NumChars; Pos ++)
		{
			if(
				(!isdigit(Address[Pos]))
				&& ((Address[Pos] < 'A') || (Address[Pos] > 'Z'))
				&& (Address[Pos] != '_')
				&& (Address[Pos] != '.')
				&& (Address[Pos] != '@')
				&& (Address[Pos] != '-'))
			{
				RtnVal = FALSE;
			}
		}
	}
	return RtnVal;
}

BOOL ValidatePhone(CString FaxNum)
{
	BOOL		RtnVal = TRUE;

	if(FaxNum.GetLength() != 11)
	{
		RtnVal = FALSE;
	}
	else
	{
		int		Pos;
		int		NumChars;

		NumChars = FaxNum.GetLength();
		FaxNum.MakeUpper();

		for(Pos = 0; Pos < NumChars; Pos ++)
		{
			if(!isdigit(FaxNum[Pos]))
			{
				if(!isspace(FaxNum[Pos]))
					RtnVal = FALSE;
			}
		}
	}
	return RtnVal;
}

Issues

The e-mail rules will need to change when the new domain names become available