Growing your business is growing your brand name.
a Domain name is a brand. Your domain name is YOUR BRAND.
You should use your brand everywhere and as frequently as possible for your brand email as well as your brand website or web application (wordpress/joomla/wiki/moodle/etc)
when you send email from your brand or domain, your brand name (domain name) is seen by the recipient(s)
when someone wants to send your brand an email, they have to either type or click on your domain or brand email address, they see your name and your brand.
when you write about your brand on your social media account, readers should be able to visit your web application or website, by clicking through to your domain name, website or web application.
Building your brand name is all about marketing and communicating about your brand and your domain name. Print your domain name email address and your domain name website on your business cards, on bumper stickers, on your letter heads, Invoices, Quotes, social media accounts and, well everywhere and anywhere!