Now I rejoice in what I am suffering for you, and I fill up in my flesh what is still lacking in regard to Christ’s afflictions, for the sake of his body, which is the church. 25 I have become its servant by the commission God gave me to present to you the word of God in its fullness— (Colossians 1:24-25 NIV)
True evangelists are servants of the church. They have been given understanding of the word of God, and are therefore responsible to tell the message to those whom Jesus has died. They must see themselves as servants of those who are willing to listen and believe.
But there are false evangelists who only pretend to serve the church; they are really just serving themselves:
For, as I have often told you before and now tell you again even with tears, many live as enemies of the cross of Christ. 19 Their destiny is destruction, their god is their stomach, and their glory is in their shame. Their mind is set on earthly things. (Philippians 3:18-19 NIV).