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

Calculating dependencies ... done!
Dependency resolution took 1.00 s (backtrack: 0/20).

[ebuild  N     ] acct-group/stalwart-mail-0::gentoo  0 KiB
[ebuild  N     ] acct-user/stalwart-mail-0::gentoo  0 KiB
[ebuild  N     ] net-mail/stalwart-mail-0.16.15::gentoo  USE="rocks sqlite -debug -mysql -postgres" 86334 KiB

Total: 3 packages (3 new), Size of downloads: 86334 KiB