in the webassist/mail/mailformating_php.php file, change line 164:
$knownDomsPat = "/^(com|net|org|edu|int|mil|gov|arpa|biz|aero|name|coop|info|pro|museum|cat|\w{2,2})$/i";
to:
$knownDomsPat = "/^(com|net|org|edu|int|mil|gov|arpa|biz|aero|name|coop|info|pro|museum|cat|it|\w{2,2})$/i";