This second death is not … the dissolution or annihilation of both spirit and body, but banishment from the presence of God and from partaking of the things of righteousness.
It is very clear in the Doctrine and Covenants 76:30–37, that the only persons who will be completely overcome by this dreadful fate [the second death] are the sons of perdition, who go with the devil and his angels into ‘outer darkness.’ All the rest of mankind, even the wicked, will receive some measure of salvation after they suffer the wrath of God. However, they will of necessity be brought to repentance and acceptance of the gospel of Jesus Christ as far as it will apply to them.
(Joseph Fielding Smith, Doctrines of Salvation, 2:222, Answers to Gospel Questions, 1:76)