HelpingHost.com offers DomainKeys or DKIM included in each web hosting plan.
DomainKeys or DKIM is an e-mail authentication system designed to verify the DNS domain of an e-mail sender and the message integrity.

SPF record hosting

The most important thing if you send email to a list of people/customers/members is that each email arrives at its recipient and does not end up in a spam folder or worse silently deleted.
The factors that determine the faith of your email list are many and very complex.
For that reason the best way to maintain and use your email list is with a company that specializes in the field.
Affordable E-Mail Marketing for everybody. With tiered plans starting at just $9.95 per month, our pricing structure is designed to make certain that regardless of your business size, you can capitalize on the revenue-generating power of email marketing.

The Power of Google Postini

Postini protects more than 35,000 businesses worldwide from a wide range of email, instant messaging (IM) and Web threats, and provides message archiving and encryption — all from one unified platform. With Postini's integrated suite of on-demand services, your business can manage all message security, enforce corporate policies, and ensure regulatory compliance across any size organization.