To configure your sending domain navigate to the DNS Configuration tab. Enter a valid domain that you own and click create. This will be the domain that emails sent from your site come from. (Example.com)
Once you click create a DNS Record will be generated. This DNS Record is used to verify ownership of your domain. You will need to make DNS configuration changes through your domain registrar (or DNS provider) for your sending domain. You must add a TXT record to your domain with the generated hostname and value.
Some providers are particular about how the hostname is entered, so please check with your domain provider to see if there are any special requirements for entering your DNS TXT record.
Here are some how-to documents for editing DNS records with common DNS providers:
To verify that the DNS records were entered correctly click verify DNS on the DNS configurations tab in the plugin.
If your domain does not verify it could be that the DNS Record has not propagated. It can take up to 24 hours for the DNS to propagate.