If you manage your own DNS (even if you don’t), you should definately create an SPF (sender policy framework) record for your domain. It helps in the prevention of SPAM and has been widely adopted by AOL, Yahoo, Gmail, Hotmail, etc. Microsoft has an easy online wizard to help you create your own SPF record.
Your webhost may have a pre-canned SPF record for you already. As well, email only hosts like Fastmail, are extremely versed in this area and probably have a very robust SPF record already created for you to copy/paste.
