Paul, Silvanus, and Timothy,
To the church of the Thessalonians in God our Father and the Lord Jesus Christ:
Grace to you and peace from God our Father and the Lord Jesus Christ.
We must always give thanks to God for you, brethren, as is right, because your faith is growing abundantly, and the love of every one of you for one another is increasing. Therefore we ourselves boast of you among the churches of God for your steadfastness and faith during all your persecutions and the afflictions that you are enduring.
That was encouraging and reassuring wasn't it? Our Sunday morning pewsitters will likely smile and nod at that one.
To this end we always pray for you, asking that our God will make you worthy of his call and will fulfil by his power every good resolve and work of faith, so that the name of our Lord Jesus may be glorified in you, and you in him, according to the grace of our God and the Lord Jesus Christ.
But they will just hear the fluff plucked from the letter's intro, the meat gets let out. In verses 5-10 they would have heard about God's vengeance on those who do not obey the gospel of Jesus, and they should have heard about eternal damnation too,
5 This is evidence of the righteous judgement of God, and is intended to make you worthy of the kingdom of God, for which you are also suffering. 6 For it is indeed just of God to repay with affliction those who afflict you, 7 and to give relief to the afflicted as well as to us, when the Lord Jesus is revealed from heaven with his mighty angels 8 in flaming fire, inflicting vengeance on those who do not know God and on those who do not obey the gospel of our Lord Jesus. 9 These will suffer the punishment of eternal destruction, separated from the presence of the Lord and from the glory of his might, 10 when he comes to be glorified by his saints and to be marvelled at on that day among all who have believed, because our testimony to you was believed.
I cannot recall ever hearing a sermon from an Episcopal church pulpit in which the reality of eternal damnation was preached. In fact, I recall one sermon in which that fact was denied.
Thanks to our Revised Common Lectionary most pewsitters won't hear about it either.