Script para validar la entrada de la dirección de Email

function chkEmail(theAddress)
'Chequear una dirección válida
'Retorna 1 si es inválida
'Retorna 0 si es una dirección válida
dim atCnt
chkEmail = 0

'Chequear Tamaño
if len(theAddress) < 5  then
chkEmail =1

'Chequear que tenga una @
elseif instr(theAddress, "@") = 0 then
chkEmail = 1

'Chequear que exista un punto
elseif instr(theAddress, ".") = 0 then
chkEmail = 1

'Chequear la cantidad de caracteres
elseif len(theAddress) - instrrev(theAddress, ".") > 3 then
chkEmail = 1

'Chequear que no exista "_" después de la @
elseif instr(theAddress, "_")  <> 0 and instrrev(theAddress, "_") > instrrev(theAddress, "@") then
chkEmail = 1

else
atCnt = 0

for i  = 1 to len(theAddress)
  if mid(theAddress,i,1) = "@"  then
  atCnt = atCnt + 1
end if
next

if atCnt > 1 then
 chkEmail = 1
end if

'Chequear cada caracter
for i = 1 to len(theAddress)
if not isnumeric(mid(theAddress,i,1)) and (lcase(mid(theAddress,i,1)) < "a" lcase(mid(theaddress,i,1) > "z") and mid(theAddress,i,1) <> "_" and mid(theAddress,i,1) <> "." and mid(theAddress,i,1) <> "@" and mid(theAddress,i,1) <> "-" then

chkEmail = 1
end if
next
end if
end function