Dovecot failed to start

Hi,

I have problem with dovecot using lmtp, when I start dovecot, I get the following status:

● dovecot.service - Dovecot IMAP/POP3 email server
Loaded: loaded (/usr/lib/systemd/system/dovecot.service; enabled; vendor preset: disabled)
Active: failed (Result: exit-code) since Sat 2020-12-19 21:52:05 WIB; 13min ago
Docs: man:dovecot(1)
http://wiki2.dovecot.org/
Process: 2070583 ExecStart=/usr/sbin/dovecot -F (code=exited, status=89)
Process: 2070577 ExecStartPre=/usr/libexec/dovecot/prestartscript (code=exited, status=0/SUCCESS)
Main PID: 2070583 (code=exited, status=89)

Dec 19 21:52:05 server.fitinline.com systemd[1]: Starting Dovecot IMAP/POP3 email server…
Dec 19 21:52:05 server.fitinline.com systemd[1]: Started Dovecot IMAP/POP3 email server.
Dec 19 21:52:05 server.fitinline.com dovecot[2070583]: Error: service(lmtp): Socket already exists: /var/spool/postfix/private/lmtp
Dec 19 21:52:05 server.fitinline.com dovecot[2070583]: Fatal: Failed to start listeners
Dec 19 21:52:05 server.fitinline.com dovecot[2070583]: master: Error: service(lmtp): Socket already exists: /var/spool/postfix/private/lmtp
Dec 19 21:52:05 server.fitinline.com dovecot[2070583]: master: Fatal: Failed to start listeners
Dec 19 21:52:05 server.fitinline.com systemd[1]: dovecot.service: Main process exited, code=exited, status=89/n/a
Dec 19 21:52:05 server.fitinline.com systemd[1]: dovecot.service: Failed with result 'exit-code'.

Does anyone have the same experience? How to fix this?
Thanks!