Event ID 12016
KB ID 0000292 Problem Event ID 12016 There is no valid SMTP Transport Layer Security (TLS) certificate for the FQDN of <domain>. The existing certificate for that FQDN has expired. The continued use of that FQDN will cause mail flow problems. A new certificate that contains the FQDN of <domain> should be installed on this server as soon as possible. You can create a new certificate by using the New-ExchangeCertificate...