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

Calculating dependencies ... done!
Dependency resolution took 1.55 s (backtrack: 0/20).

[ebuild  N     ] dev-db/lmdb-0.9.36:0/0.9.36::gentoo  USE="-static-libs" 147 KiB
[ebuild  N     ] acct-group/postfix-0-r3::gentoo  0 KiB
[ebuild  N     ] acct-group/postdrop-0-r3::gentoo  0 KiB
[ebuild  N     ] acct-user/postfix-0-r3::gentoo  0 KiB
[ebuild  N     ] mail-mta/postfix-3.11.7::gentoo  USE="eai lmdb pam sqlite ssl -berkdb -cdb -dovecot-sasl -ldap -ldap-bind -mbox -memcached -mongodb -mysql -nis -postgres -sasl (-selinux) -tlsrpt -verify-sig" 5170 KiB
[uninstall     ] mail-mta/nullmailer-2.2-r2::gentoo  USE="ssl -test" 
[blocks b      ] mail-mta/postfix ("mail-mta/postfix" is soft blocking mail-mta/nullmailer-2.2-r2)
[blocks b      ] mail-mta/nullmailer ("mail-mta/nullmailer" is soft blocking mail-mta/postfix-3.11.7)

Total: 5 packages (5 new, 1 uninstall), Size of downloads: 5317 KiB
Conflict: 2 blocks (all satisfied)