I Corinthians 1:1

Paul called to be an apostle of Jesus Christ through the will of God, and Sosthenes our brother...
(KJV)

Then: The verse shows the normal letter style of the New Testament era. Element 1: Tell the reader who is sending it. The Corinthians knew Paul; however, he wanted to remind them that he was an apostle thoroughly dependent and obedient to his Lord. Apostle? Called by God he had seen the risen Lord and had been sent to tell others. Part of Paul's job was to check up on those he taught and be sure they understood the essentials about Christ. This letter is evidence of Paul's commitment to Christ.

Who is Sosthenes? Our brother. Believers will meet him in heaven. The book, Historical Commentary on First Corinthians by William M. Ramsay (partially available as a google book) says he had to be a reputable person, possibly a teacher whom the Corithians respected. He may be the same guy mentioned in Acts, but nobody knows.

Now: Email is the way to go. Unintentionally, they mimic first century letter style. Up front there's the sender and the topic. Up front I can read or delete. Or I can wait to check it later. Paul's letters had to be like email from family members. Read them first, store in a folder, and read again.

Today's apostles are called missionaries. They may not have seen the risen Lord, but they've heard his call and have seen his work in their lives. They know him and serve him no matter the cost. They're always on the lookout for others to work alongside. They have their own "Sosthenes."

Extra Sources: Historical Commentary on First Corinthians by William M. Ramsay, ed. by Mark W. Wilson, Kregel Publications, c 1996. online at http://books.google.com/books?id=J7RyILzCn8UC&dq=Ramsay+Corinthians&printsec=frontcover&source=bl&ots=dwdPJmUUh6&sig=G9Pe1_oY5izKuYc4bC9gnVjRdds&hl=en&ei=6SYdS665B5Tl8QaI4dHeAw&sa=X&oi=book_result&ct=result&resnum=6&ved=0CBQQ6AEwBTgK#v=onepage&q=&f=false
Commentary on the Whole Bible (Acts to Revelation) by Matthew Henry, see: http://www.ccel.org/ccel/henry/mhc6.titlepage.html