dovecot - Apr 2018 - Warning message about quota.conf

Hi, 

In my maillog I see this warning message at every reception of e-mail: 

_STATUS=SENT (DELIVERED VIA DOVECOT SERVICE (DOVECONF: WARNING:
/ETC/DOVECOT/CONF.D/90-QUOTA.CONF LINE 39: GLOBAL SETTING MAIL_PLUGINS
WON'T CHAN....._ 

It is just a warning, the e-mail was delivered. 

I don't find where is the problem. 

Thank's.
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