DysonLive

Postinst runs update-exim4.conf
update-exim4.conf runs exim4: /usr/sbin/exim4 -C /var/lib/exim4/config.autogenerated.tmp -bV

truss of exim4:

20576:  access("/etc/gcrypt/fips_enabled", F_OK)        Err#2 ENOENT
20576:  open("/proc/sys/crypto/fips_enabled", O_RDONLY) Err#2 ENOENT
20576:  brk(0x00755FC0)                                 = 0
20576:  brk(0x00759FC0)                                 = 0
20576:  access("/dev/random", R_OK)                     Err#13 EACCES [file_dac_read]
20576:  fstat(2, 0xFFFFFD7FFFDFEE80)                    = 0
Fatal: 20576:   write(2, " F a t a l :  ", 7)                   = 7
no entropy gathering module detected

Before accessing /dev/random exim4 sets uid to Debian-exim, which has no file_dac_read privilege.

Run devfsadm -P.