Internet-Security.com TCP port 4190 details

TCP port 4190 is the IANA-registered port for the ManageSieve protocol (RFC 5804), used to manage Sieve email filtering scripts on mail servers.
Dovecot exposes ManageSieve on 4190 via its Pigeonhole plugin, letting users upload and edit Sieve rules.
The Cyrus IMAP server provides its timsieved/ManageSieve service on port 4190 for managing user Sieve scripts.
Webmail clients commonly use this port to manage filters, including Roundcube’s managesieve plugin and Horde’s Ingo module when connected to Dovecot or Cyrus.
Many production mail stacks deploy 4190 specifically for ManageSieve access, replacing the older unofficial port 2000 historically used by early timsieved setups.

TCP 4190