Months before Salesforce.com Inc. considered buying Twitter Inc., the company was looking at more than a dozen acquisition targets that didn’t include the social-media giant, according to an internal presentation for its board members.

The presentation came from a trove of thousands of former Secretary of State Colin Powell’s emails that was published in September by DCLeaks, a website of self-described “hacktivists” that releases documents from government officials and other prominent people. Mr. Powell sits on Salesforce’s...