Open-relay is the third-party relaying of email messages though a mail server. Spammers looking to obscure or hide the source of large volume mailings often use mail servers with open-relay vulnerabilities to deliver their email messages.

Combining Email Marketing with Other Types of Marketing
Whether you choose to do your marketing online or offline, one thing does not change. This is the concept that no single marketing strategy will be as effective as a combination of two or more marketing strategies.