sendmail -> lmtp 501 5.6.0 Data format error

[Marc Roos]

When changing in a working setup sendmail.mc 

From this
MAILER(smtp)dnl
MAILER(procmail)dnl

To this
FEATURE(`local_lmtp',`[IPC]',`FILE /var/run/dovecot/lmtp')dnl
MAILER(local)dnl

I am getting these errors '501 5.6.0 Data format error' and ' 
Unrecognized host name'. 

What should I change in my lmtp config? Could this be related that 
messages are being relayed from other servers?

lmtp_address_translate =
lmtp_hdr_delivery_address = final
lmtp_proxy = no
lmtp_rcpt_check_quota = no
lmtp_save_to_detail_mailbox = no
lmtp_user_concurrency_limit = 0