These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 1.08 s (backtrack: 0/20).

[ebuild  N     ] acct-group/dovecot-0-r3::gentoo  0 KiB
[ebuild  N     ] acct-group/dovenull-0-r3::gentoo  0 KiB
[ebuild  N     ] acct-user/dovecot-0-r3::gentoo  0 KiB
[ebuild  N     ] acct-user/dovenull-0-r3::gentoo  0 KiB
[ebuild  N     ] net-mail/dovecot-2.4.2-r3:0/2.4.2::gentoo  USE="pam sqlite -argon2 -cdb -kerberos -ldap -lua -lz4 -managesieve -mysql -postgres (-selinux) -sieve -solr -static-libs -stemmer -suid -system-icu (-systemd) -test -textcat -unwind -verify-sig -xapian -zstd" LUA_SINGLE_TARGET="-lua5-3 -lua5-4" 7625 KiB

Total: 5 packages (5 new), Size of downloads: 7625 KiB