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

Calculating dependencies ... done!
Dependency resolution took 1.10 s (backtrack: 0/20).

[ebuild  N     ] dev-cpp/cli11-2.7.2::gentoo  USE="-doc -test" 1414 KiB
[ebuild  N     ] dev-libs/gmime-3.2.15-r2:3.0::gentoo  USE="crypt -doc -idn -test -vala" 2182 KiB
[ebuild  N     ] dev-libs/xapian-2.1.0:0/45::gentoo  USE="-debug -static-libs -verify-sig" CPU_FLAGS_X86="sse sse2" 3439 KiB
[ebuild  N     ] net-mail/mu-1.14.0::gentoo  USE="readline -emacs -test" 764 KiB

Total: 4 packages (4 new), Size of downloads: 7797 KiB