Twitter has officially become the most linked to social media outlet in email marketing campaigns, according to Email Data Source.

To date in 2009 the number of campaigns with Twitter links has grown to 41,399 and 41,052 for Facebook. Twitter officially passed Facebook and became the most linked to social media outlet in March of 2009. During March, Email Data Source recorded 4,408 email campaigns which linked to Twitter and 4,292 email campaigns with links to Facebook.

“In the data Email Data Source has been tracking, there has been a dramatic increase in the number of email marketing campaigns that contain links to Facebook and Twitter,” said Bill McCloskey, chairman and co-founder of Email Data Source.

Since March, Twitter has continued to dominate the email marketplace by being the most prominently linked to website, and the gap between Twitter and Facebook has grown. In June, Twitter was linked to in 9,506 campaigns and Facebook was linked to in 8,636 campaigns.

The first email campaign with a link to twitter.com tracked by Email Data Source was in 2007, and for all of 2007, there were a total of 215 email marketing campaigns that linked to the site. During that same year, there were 729 campaigns that linked to Facebook. In 2008, the number of campaigns containing Twitter links grew by 1081% (to 2,540 campaigns) and 1635% (to 12,650 campaigns) for Facebook.