Typically in the middle of a sentence, if you are using a job title after a name, it is not capitalized. For example, "George Washington was the president of the United States." or "He is the chief executive officer of Google." But, if you use the title directly before the name, it is capitalized. For example, "She waved to President Washington."

When you address the envelope or write the names at the top of a business letter, the job title is capitalized because it isn't a part of a sentence.