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

Calculating dependencies   ... done!
[ebuild  N    ] mail-mta/sendmail-8.14.0  USE="sasl sockets ssl tcpd -ipv6 -ldap -mailwrapper -mbox -nis" 2,009 kB 
[ebuild  N    ] mail-filter/dkim-milter-2.5.5  USE="-diffheaders -ipv6" 632 kB 
[blocks B     ] mail-mta/sendmail (is blocking mail-mta/postfix-2.4.6-r2)
[blocks B     ] mail-mta/postfix (is blocking mail-mta/sendmail-8.14.0)

Total: 2 packages (2 new, 2 blocks), Size of downloads: 2,640 kB