Particularly in the case of the New Testament letters, such outlines can help us understand the flow of the arguments made by their writers.
The outline of First Thessalonians presented by some scholars seems far too detailed to me. I like the one in The Jerome Bible Commentary (I have an older edition than the one hyperlinked here), produced by Roman Catholic scholars:
(I) Paul's Personal Relations with the Thessalonians (1:1-3:13)
(A) When the Church Was Being Founded (1:2-2:16)(II) Instructions and Exhortations (4:1-5:24)
(B) Since the Foundation of the Church (2:17-3:13)
(A) Holiness and Chastity (4:1-8)(III) Conclusion (5:25-28)
(B) Charity and Order (4:9-12)
(C) The Fate of Departed Christians (4:13-18)
(D) The Date of the Parousia [Christ's return, the Day of the Lord] (5:1-11)
(E) Exhortations for Community Living (5:12-24)
The Jerome Commentary notes this about the founding of the church at Thessalonica:
"As usual, Paul's success with [his fellow] Jews was minimal. After three Sabbaths in the synagogue, he apparently centered his activity in the house of a certain Jason. A large number of the 'God-fearing' Greeks, along with many pagans...and important women, were converted. The Jews, however, jealous of Paul's success, stirred up a mob against the missionaries and forced their expulsion from the city (Acts 17:1-9)..."Pauls' stay in Thessalonica is thought to have lasted only two or three months.
By the way, God-fearers is a formal term that was used of Gentiles, non-Jews, who believed in the God of the Jewish people--Who is also the God of Christianity--and worshiped regularly with the Jews in the synagogues.
Greeks was a term used not necessarily of people who were ethnically Greek, but who were non-Jews who were culturally Greek. That is, they bore Greek names; they used the Greek language, the Mediterranean basin's second language, the tongue of commerce and scholarship; and they basically thought from the vantage point of the Greek philosophical mindset. Rome had conquered Greece and then Greek culture largely conquered Rome.
I do hope to post a verse-by-verse exploration of First Thessalonians later. But a little more background seemed warranted.
[For the first installment, look here.]