Check if 2 emails in match in tsql

compare-emails.sql

-- Written for TSQL
CREATE FUNCTION dbo.CompareEmails(
	@Email1 AS NVARCHAR(MAX) = '', 
	@Email2 AS NVARCHAR(MAX) = ''
)
RETURNS BIT
AS
BEGIN
	-- Basic check to see if each string is an email
	IF LEN(@Email1) = 0
	OR LEN(@Email2) = 0
	OR CHARINDEX('@', @Email1) < 1
	OR CHARINDEX('@', @Email2) < 1
		RETURN 0

	-- Emails are case insensitive so convert them to lowercase
	SET @Email1 = LOWER(@Email1)
	SET @Email2 = LOWER(@Email2)

	-- Get the index of the '@' characters to split the emails
	DECLARE
	@AtIndex1 AS int = CHARINDEX('@', @Email1),
	@AtIndex2 AS int = CHARINDEX('@', @Email2)

	-- Split the emails into front and tail sections for comparison
	DECLARE
	@Email1Start AS NVARCHAR(MAX) = LEFT(@Email1, @AtIndex1 - 1),
	@Email2Start AS NVARCHAR(MAX) = LEFT(@Email2, @AtIndex2 - 1),
	@Email1End AS NVARCHAR(MAX) = RIGHT(@Email1, LEN(@Email1) - @AtIndex1),
	@Email2End AS NVARCHAR(MAX) = RIGHT(@Email2, LEN(@Email2) - @AtIndex2)

	-- In emails, any '.' characters in the username section of an email are optional so remove them
	SET @Email1Start = REPLACE(@Email1Start, '.', '')
	SET @Email2Start = REPLACE(@Email2Start, '.', '')

	DECLARE @Match AS BIT = 
		CASE WHEN
			@Email1Start = @Email2Start
			AND @Email1End = @Email1End
		THEN 1
		ELSE 0
		END
         
	RETURN @Match;
END;