Client sent invalid input for CATEGORY

8 Jul 2026


      Hello list
We are running a dovecot 2.4 instance and the following errors start to
pop up after a listener is configured to scrape metrics with Prometheus:
... dovecot[2090309]: stats: Error: conn unix:stats
(pid=2090333,uid=108): Client sent invalid input for CATEGORY: Category
parent 'ssl' changed to 'ssl' (input: CATEGORY        ssl-client        ssl)
Stats listener config:
service stats {
inet_listener http {
port = 9090
ssl = yes
}
}
So far I failed to reliably trigger the error messages and it looks like
they appear randomly.
Besides the logged errors, everything seems to work correctly.
Could this be a possible bug, or configuration error?
Kind regards,
Patrik

Client sent invalid input for CATEGORY

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