After upgrading my mail server to Fedora 27, dovecot (IMAP server) does not work properly - it runs, but clients can't refresh folders reliably. This seems to be caused by SELinux denials like this:

Nov 22 11:40:18 mail.happyassassin.net audit[838]: AVC avc:  denied  { map } for  pid=838 comm="imap" path="/home/adamw/Maildir/dovecot.index" dev="vda3" ino=942391 scontext=system_u:system_r:dovecot_t:s0 tcontext=system_u:object_r:mail_home_rw_t:s0 tclass=file permissive=0

There are many denials for 'dovecot.index' files in various subdirectories (which represent mail folders, in maildir-style mail storage).

There are also similar denials for dovecot.index.log files, e.g.:

Nov 22 11:40:21 mail.happyassassin.net audit[838]: AVC avc:  denied  { map } for  pid=838 comm="imap" path="/home/adamw/Maildir/.Blog/dovecot.index" dev="vda3" ino=936911 scontext=system_u:system_r:dovecot_t:s0 tcontext=system_u:object_r:mail_home_rw_t:s0 tclass=file permissive=0