The function validate_email in lib/weblib.php doesn't validate emails of the form

firstname.lastname@host.organization.com

according to the function there may only be a country level domain and a top level domain, so only

firstname.lastname@organization.com

would be accepted, which is due to the regular expression:

return (ereg('^{[-!#$%&\'*+
./0-9=?A-Z}_`a-z

~]+\.'.

'[-!#$%&\'*+
./0-9=?A-Z^_`a-z

~]+$',

$address));