Yes. From the 'Create mailbox' page, enter the email address you wish to use but then select 'use a domain I've registered elsewhere' from the drop down.
Enter your domain name and click 'create mailbox'.
Once you've done this your Smarta Business Builder email address and inbox will be set up to use the domain you've selected, but it won't work until you've made some changes to your mail settings with your domain host.
You will need to log in to your domain host, access your control panel and find your MX records. You need to create a new MX record and point it to MX.MAILANYONE.NET. with the MX-pref or prio set to 1.
You can check your DNS Settings by logging into the who.is
website -http://who.is/dns - then
search for your website.
Your DNS Settings should look like this: