Nowadays, many user use Google Apps for their own domain such as mickgenie.com but they do not know Google Apps did allow them to apply SPF (Sender Policy Framework) to their email to protect spamming issue.
By using SPF records, it allow domain owners to specify which hosts are permitted to send email on behalf of their domains. Normal SMTP allows any computer to send an email claiming to be from anyone. Thus, it’s easy for spammers to send emails with forged From: addresses. SPF allows a domain owner to use a special format of DNS TXT records to specify which machines or hosts are authorized to transmit email for their domain; this makes it difficult to forge From: addresses.
To set your domain’s SPF record, you should have access to your domain’s DNS settings. On your DNS resource, publish the following TXT record: v=spf1 include:aspmx.googlemail.com ~all