Mailserver offline reported but it is online

they are reported offline, and still work.

TLS is enabled for those mail servers, and in such cases the Protector checks traffic through port 465, unless a different port is specified.

​
However there may be cases where mail servers use the TLS protocol through port 25, and this is the case. For example, mail server is not listening on port 465, but is listening on port 25, offering STARTTLS:

This tricks the Protector into thinking there is no connection, since it performs connection check on port 465.

To fix the wrong display, I suggest explicitly setting the port number to 25 for such mail servers.

In firmware 56, the default port number for sending mail when TLS is ON, is 465 if not specified. Setting it explicitly to 25 has fixed the red status on mail.