- Plesk for Linux
- Plesk for Windows
Connection by IMAP/SMTP protocol using mail client results in the following warning:
PLESK_ERROR: Unable to verify the mail server identity
- Default certificate was set in Plesk > Tools & Settings > SSL/TLS certificate > Certificate for securing mail
Default self-signed SSL/TLS certificate was set for securing a mail server.
Change SSL/TLS certificate to either a free SSL/TLS certificate from Let's Encrypt or an SSL/TLS certificate purchased from a certificate authority.
Refer to the following link on documentation portal to get additional information on how to acquire and install SSL/TLS certificates for Plesk and a mail server: Securing Plesk and the Mail Server With SSL/TLS Certificates .