A customer is trying to configure Outlook to work with their Exchange mailbox via POP or IMAP protocol with SSL/TLS encryption. Outlook's verification tests fail with the following error message:
Send test e-mail: Your server does not support the connection encryption type specified. Try changing the encryption method. Contact the administrator of the mail server or Internet service provider for further assistance.
Checking the Event Viewer on Exchange hub transport server, you can see the following messages when Outlook is trying to connect:
Microsoft Exchange could not find a certificate that contains the domain name <domain.tld> in the personal store on the local computer. Therefore, it is unable to support the STARTTLS SMTP verb for the connector Client EXHUB01 with a FQDN parameter of <domain.tld>. If the connector's FQDN is not specified, the computer's FQDN is used. Verify the connector configuration and the installed certificates to make sure that there is a certificate with a domain name for that FQDN. If this certificate exists, run Enable-ExchangeCertificate -Services SMTP to make sure that the Microsoft Exchange Transport service has access to the certificate key.
The customer configured server with the hostname domain.tld to be their SMTP server (the exact hostname is mentioned in the provided above error message in the Event Viewer), and there is no certificate for domain.tld installed on the Exchange hub transport servers.
You have to install the appropriate certificate on Exchange hub servers.