Nearly all of them were. Paul’s epistles to Timothy, Titus, and Philemon were written to individuals, but meant to be read also to the community they were the head of (in the case of Philemon the epistle is also addressed to Apphia, Archippus, and “to the church in your house”). It is possible to read James’s “twelve tribes in the Dispersion” as referring to the entire Church, but more likely it refers specifically to those Christians outside of Jerusalem or specifically to Jewish Christians outside of the Holy Land. 2 John’s “elder lady” probably represents a particular church community, perhaps that of Ephesus.
What we are left with is 2 Peter, which does not make its recipients clear, 1 John, which hardly qualifies as an epistle at all though it is traditionally counted among them, 3 John, which is to just one specific person (Gaius), and Jude, which seems to be written for all Christians. All the rest of the epistles are written to specific groups.