To securely exchange mail data with Plesk server, you may need to install custom SSL/TLS certificates on the Plesk server. Specifically, SSL/TLS certificates can be installed for the Qmail mail transfer agent and the Courier-IMAP mail server that supports the IMAP and POP3 protocols.

To install custom SSL/TLS certificates, you need to download the certificates to the Plesk server and then replace the installed default SSL/TLS certificates for Qmail and Courier-IMAP servers with the downloaded custom certificates.

This section describes procedures for installing custom SSL/TLS certificates for Qmail and Courier-IMAP servers.