Mail client shows warning connecting to Plesk mail server: the server to which you are connected uses a security certificate that can not be verified. The main destination name is not valid –
![How to secure a Plesk mail server with an SSL certificate (Let's Encrypt / other certificate authorities) – Plesk Help Center How to secure a Plesk mail server with an SSL certificate (Let's Encrypt / other certificate authorities) – Plesk Help Center](https://support.plesk.com/hc/article_attachments/360029693474/Screenshot_2019-03-26_SSL_TLS_Certificates_-_Plesk_Onyx_17_8_11_1_.png)
How to secure a Plesk mail server with an SSL certificate (Let's Encrypt / other certificate authorities) – Plesk Help Center
![SSL related mail server issue - Multiple domails - aaPanel - Hosting control panel. One-click LAMP/LEMP. SSL related mail server issue - Multiple domails - aaPanel - Hosting control panel. One-click LAMP/LEMP.](https://images.guru/images/2020/08/28/Qt2FR.jpg)