Hey @milespearce
Your ‘a’ record points to the server which hosts your Discouse instance.
A different type of DNS record called an ‘mx’ or Mail eXchange will point to the whereabouts of your email.
If you’re using the mail receiver then your MX record would point at the FQDN (Fully Qualified Domain Name) of your Discourse instance, otherwise it will point at the mail provider you’ve selected.