There are only a few times when job titles should be capitalized. Most of the time, they shouldn’t. You do capitalize a job title  when it precedes the persons’s name, essentially becoming a part of the name:

"Executive Vice President Michelle Williams will attend."
"Please forward all correspondence to Chancellor McAdams."

And even if the title precedes the name, if the title is preceded by an article (a, an, the), the title does not get capitalized:

"The head of mechanical engineering, Bob Cotterpin, is a nice guy."