After upgrading my mail server from Fedora 26 to 27, I see a Postfix-related denial which I believe is new:

Nov 22 11:40:15 mail.happyassassin.net audit[670]: AVC avc:  denied  { read } for  pid=670 comm="newaliases" name="dynamicmaps.cf.d" dev="vda3" ino=705901 scontext=system_u:system_r:sendmail_t:s0 tcontext=system_u:object_r:postfix_etc_t:s0 tclass=dir permissive=0

This I think is postfix's /usr/bin/newaliases being run on startup, trying to access the /etc/postfix/dynamicmaps.cf.d directory. I'm assuming this will prevent postfix from properly handly newly-created dynamic maps, or something along those lines.