Cyrus 2.4 and vacation problem (smtputf8)

[Josef Karliak]

Good morning,
I upgraded servers to new Postfix versions, we had some issue with
bounced vacation with czech characters. But postfix has smtputf8 support
enabled :
smtputf8_enable = yes
smtputf8_autodetect_classes = sendmail, verify

and the issue with emails (vacation) persists.
After some checking I've found that thereis not postfix that bounce
the message - it is cyrus'es LMTP, listenning on TCP/24:
Sep 13 08:08:12 postman11 postfix/cleanup[2916]: 59F2A280DB7:
message-id=<cmu-sieve-2580-1536818892-***@postman11>
Sep 13 08:08:12 postman11 postfix/qmgr[2885]: 59F2A280DB7: from=<>,
size=658, nrcpt=1 (queue active)
Sep 13 08:08:12 postman11 postfix/lmtp[2918]: 55497280DB5:
to=<***@postman.domain.cz>, orig_to=<***@domain.cz>,
relay=postman.domain.cz[1.2.3.101]:24, delay=0.04, delays=0/0/0/0.04,
dsn=2.1.5, status=sent (250 2.1.5 Ok
SESSIONID=<postman11-2580-1536818892-1>)
Sep 13 08:08:12 postman11 postfix/qmgr[2885]: 55497280DB5: removed
Sep 13 08:08:12 postman11 postfix/lmtp[2918]: 59F2A280DB7:
to=<***@postman.domain.cz>, orig_to=<***@domain.cz>,
relay=postman.domain.cz[1.2.3.101]:24, delay=0.11, delays=0/0/0.1/0,
dsn=5.6.7, status=bounced (SMTPUTF8 is required, but was not offered by
host postman.domain.cz[1.2.3.101])
Sep 13 08:08:12 postman11 postfix/qmgr[2885]: 59F2A280DB7: removed

So do I need to set something in cyrus config ? What did I missed ?
Thanks and best regards
J.Karliak