421 Too many concurrent SMTP connections; please try

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421 Too many concurrent SMTP connections; please try

The server gives me this error, I need to solve it, do you know how? It would be to increase some parameter

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Logs ?

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Now I have the same issue with one of my VPS user. I’m checking logs, but anyone find the reason or solution yet? Thanks!

Update: I realized “refused: too many connections” in /var/log/mainlog, restarted server and SMTP works.