Luigi Rosa wrote:

...

Nov 22 13:06:56 grover dovecot: imap-login: Disconnected (no auth attempts): rip=192.168.2.3, lip=192.168.2.5, TLS: Disconnected

every second on my CentOS-6.4 server. Is this purely an informational message? Or is it an error message? And in either case, how can I stop the flood of messages?

If 192.168.2.3 is a Windows host, it could be infected; had a similar issue with one of my customers.

Thanks for your response. But in fact it is a Linux laptop, running KMail.

In any case, that log entry says that 192.168.2.3 is opening a TCP connection to IMAP port of 192.168.2.5 and closing it without any IMAP handshake

I've managed to stop the flood, though I'm not sure which of the steps I took had this effect. 1) I created a self-signed certificates /etc/pki/dovecot/certs/dovecot.pem and /etc/pki/dovecot/private/dovecot.pem on the server, and copied the first to /etc/pki/dovecot/certs and /etc/pki/tls/certs on the laptop. (I already had standard signed TLS certificates on both.)

2) I found that KMail on the laptop had the connection setting set to SSL/TLS on port 993, which I changed to STARTTLS on port 143.

3) I re-started dovecot on the server

4) I re-booted the laptop.

Now the flood of messages in /var/log/maillog seems to have stopped.