Some users have unique last name in the address book (e.g. ben.lao@abc.com), my question is why I send lao@abc.com , the mail will deliver to the mail box of ben.lao@abc.com.
I use short name in the “local part form from” of the conversions tab of Global Domain.
This is caused by a settings in the configuration document for that server (or group of servers). Go to the Router/SMTP tab> Basics tab and then the field ‘Address Lookup’. It is probably now set to ‘fullname then local part’
I might not be 100% sure what your problem is perhaps.
What do you want to be changed or what do you want to be happening? should it be possible for everyone to be mailed using only their last name or part of their name or should it be restricted to the correct and full mail address only?
If you want to restrict it to the full mail address only then you should choose full name (only)