When validating an e-mail, the checkMX functionallity, checks if the domain has a MX registered, but some e-mail servers doesn't has a MX record and it's a valid e-mail server either.
It will be better to check if the server has the port 25 open if it doesn't has an MX record.
It could be done this way, in the CEmailValidator.
Hmm, shouldn't that have another config option? I would expect "checkMX" to do exactly and only that: Check for an MX record. Maybe "checkPort" or "checkSmtpPort"?