this was fixed afaik, any more actions needed or ticket can be closed?

Here's the policy module I created to let dovecot run spamc in its own context:

module dovecot_postlogin 1.1;

require {
type dovecot_t;
type spamc_exec_t;
type spamc_t;
class file { ioctl read getattr lock execute execute_no_trans entrypoint open };
class process { transition signal };
}

#============= dovecot_t ==============
allow dovecot_t spamc_exec_t:file { ioctl read getattr lock execute execute_no_trans entrypoint open };
allow dovecot_t spamc_trocess { transition signal };

This is now installed on the server and makes the script work (test case created via email)

There's a legacy script that processes files in the maildir and feeds them to spamc. Since SELinux is in enforcing mode, this does not work and spamc returns with a non-zero exit code causing all mails to be discarded.