SSL server certificate problem occurred

Each day I receive this email Alert;

Subject:SSL server certificate problem occurred

Body: Warning: One or more devices cannot connect to the Sophos Mobile server (mdm.redland.qld.gov.au) because the server certificate is classified as untrusted. Verify that the configured list of SSL certificates is up to date.

 

My question;

How do I identify the devices?

How do I resolve the issue?

Will this cause any disruption to normal services?

 

 

Thanks in advance.

Phil