ESEARCH is announced but it doesn't work

[Jesus Cea]

I am using Dovecot 2.3.4. I could upgrade if necessary.

I see this capabilities after login in:

"""
a OK [CAPABILITY IMAP4rev1 SASL-IR LOGIN-REFERRALS ID ENABLE IDLE SORT
SORT=DISPLAY THREAD=REFERENCES THREAD=REFS THREAD=ORDEREDSUBJECT
MULTIAPPEND URL-PARTIAL CATENATE UNSELECT CHILDREN NAMESPACE UIDPLUS
LIST-EXTENDED I18NLEVEL=1 CONDSTORE QRESYNC ESEARCH ESORT SEARCHRES
WITHIN CONTEXT=SEARCH LIST-STATUS BINARY MOVE SNIPPET=FUZZY LITERAL+
NOTIFY SPECIAL-USE] Logged in
"""

ESEARCH (RFC 7377) seems to be available, but the command is not recognized:

"""
tag1 ESEARCH IN (mailboxes "folder1" subtree "folder2") unseen
tag1 BAD Error in IMAP command ESEARCH: Unknown command (0.001 + 0.000
secs).
"""

What am I doing wrong?

Thanks for your time and expertise.

-- 
Jesús Cea Avión                         _/_/      _/_/_/        _/_/_/
jcea at jcea.es - http://www.jcea.es/     _/_/    _/_/  _/_/    _/_/  _/_/
Twitter: @jcea                        _/_/    _/_/          _/_/_/_/_/
jabber / xmpp:jcea at jabber.org  _/_/  _/_/    _/_/          _/_/  _/_/
"Things are not so easy"      _/_/  _/_/    _/_/  _/_/    _/_/  _/_/
"My name is Dump, Core Dump"   _/_/_/        _/_/_/      _/_/  _/_/
"El amor es poner tu felicidad en la felicidad de otro" - Leibniz

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