Here are a few ways to integrate Twitter in your email strategy: 

• automatically post your email as a tweet to your company’s Twitter account. 
• include buttons in your email message which easily allows your subscribers to share your message. 
• Start a #hashtag 
• Post content on your company Twitter account: consider posting links, re-tweeting useful content and speaking with your followers. 
• Put a link to your Twitter account on the footer of your email messages; could be a button or simple link.

Read the full article here: Email Design Tip of the Week: Integrating Twitter to Your Email Strategy.