- Plesk for Linux
mail_max_userip_connections set in Plesk > Tools & Settings > Mail settings (Max connections per IP address option) is ignored?
More IP connections than configured from the same IP address are observed.
is limiting a maximum number of connections from particular user+IP, not from an IP address.
iptables "connlimit" module might be used to restrict the number of parallel TCP connections to a server per client IP address (or address block).
For more information about "connlimit" module module execute the following command:
# man iptables-extensions
Otherwise, use fail2ban to block the IP address. For more information about Fail2Ban refer to the corresponding Plesk documentation pages: