In most of his letter openings, Paul adds to his name a description or title such as “apostle of Christ Jesus” or “servant of Christ Jesus,” so it is noteworthy that he does not do that in this letter. The reason may be that in this case he was well-known to his readers (unlike in the case of Romans), and there were no questions about his apostolic authority (as in the case of Galatians and 2 Corinthians).