@tallamerican
Must I spell it out for you?
GMail is a service that anyone can sign-up for, without verifying your identity or that of the business name you place in the email address itself. That is why free email services have been used by scammers and cheaters since the inception of the internet.
Now, if you own a domain name, you can also own email addresses that go with it. So for a company to set up an email system that corresponds to their company is easy. For you, the customer, at least you know that you are dealing with the company staff and not some Nigerian guy out to get your money. You see, to have corporate email tied to your domain, you have to verify that you indeed own the WWW address in question.
To sum up: this is a law firm and undoubtedly, if you deal with them, you might send personal information. Do you know where it is going or who receives it? No you don't. In today's world of identity theft and so forth, I wouldn't trust dealing with companies through private email.
Corporate email takes minutes to set-up, so there is no excuse not to do it and it gives customers piece of mind that you are actually dealing with the company itself. Finally, I never said anything about the website itself, just commented on the use of GMail for, what seems, private and confidential correspondence, as it is usually the case when dealing with lawyers.