With so much spam clogging the internet, email deliverability is becoming a serious problem. Sender Policy Framework (SPF) is a standard created to improve things, by allowing domain name owners to specify which servers are authorized to send messages in their behalf.
To maximize the chances of your email reaching your subscribers, we recommend you give us explicit authority to send email for your domain, by including us in your "SPF record".
To set up your SPF record, go to wherever you host your internet domain name, and then look for your 'DNS settings'. In there you will find a place to edit DNS records/text records. Look for your SPF record, which might also just be called a TXT record.
If you already have an SPF record, it will look something like this:
v=spf1 a mx include:somedomain.com ~all
You need to edit this and add "include:cwmx.localharvest.org" into it. Your SPF record will now look something like this:
v=spf1 a mx include:somedomain.com include:cwmx.localharvest.org ~all
Make sure not to add a second record if you already have one, you should only have one SPF record, and while your DNS host might allow you to add a second one, this will cause deliverability problems.
If you don't have an SPF record already, you will need to manually add one, as a DNS TXT record. Make sure to include the recommended "include" portions for any other services you use to send email from your domain. For example, if you also send email via gmail, you will need to include include:_spf.google.com. If you use Constant Contact for mail broadcasts, you'll need to include include:spf.constantcontact.com as well.
For more information and details on this, we suggest you contact your website / DNS provider.
If you'd like to learn more about Sender Policy Framework, we recommend this link: http://www.openspf.org/Introduction