Whoops .... Missed a bit.
Try CHARS_FROM_RIGHT([your text attribute],LENGTH([your text attribute])-INDEX_OF('@',[your text attribute])
Explanation.
CHARS FROM RIGHT will give you the number of characters from the right that you specify with the second parameter. The problem is we don't know how many characters that is because we don't know where in the string the @ will be. That's where LENGTH and INDEX OF come into play
Lets say the email address is. Hello@itsme.com
LENGTH returns 15
INDEX OF returns 6
LENGTH minus INDEX OF will be 15 - 6. = 9
So CHARS FROM RIGHT( 'hello@itsme.com,9) should give you "itsme.com