[Dovecot] Troubles with /.dovecot.lda-dupe on dovecot 2.1.5

[Jean Michel]

Seems that is something with vacation message,

Apr 26 12:20:02 server dovecot: lmtp(26937, user at domain): Error:
file_dotlock_create(/storage/domain/users/user/.dovecot.lda-dupes) failed:
Resource temporarily unavailable
Apr 26 12:20:02 server dovecot: lmtp(26937, user at domain): Fatal: master:
service(lmtp): child 26937 killed with signal 11 (core dumps disabled)
And its created a .dovecot.lda-dupes.lock

Any idea ?
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Jean Michel Feltrin