Are you using a mac system ?
If so there is no way to create a qbw file.
using file / backup to windows creates a windows style backup file
your accountant can read that the same way he would read any other backup file. In newer versions of quickbooks they open the same place you open a qbw file. In the older versions you have to restore it.
If you are using a windows computer you have a lot more options.
You can do this a couple of different ways. It depends a little bit on what the accountant wants and a little bit on what versions you each have.
First the qbb file is a backup of your data file. The accountant should be able to open it just as easily as he can open a qbw file which is the actual data file.
If he really wants the qbw file the easiest thing to do is just copy it through windows and attach it to the email
there is also an accountants copy. That is a specialized file that will allow you to send it to him and he can make changes to the file and send it back and you can import it and all his changes will be reflected in your data file without losing what you have entered since you sent it to him. But to use that he needs a special accountants copy and a lot of accountants dont want to do that. they just want to look at your data.
You can also use something called a portable file which can be read by any version of quickbooks from any other version.
Both of the second types are more complicated than the first two.
I would suggest your simplest solution if you already have the qbb file is to tell him it is a backup file and ask him to try to open it as a backup file. Newer versions of quickbooks do that automatically if you just try to open it the same way that you would a qbw file.