Having not used my trusty Sony Ericsson K800i for a few years, I decided to see if I could use the email feature on it to send photographs (uploading to blog, Tumblr, etc.). After configuring the FastMail account credentials and SSL for IMAP4 and SMTP, I was presented with TLS/SSL server certificate not authorized by known authority. Contact your email provider.
To fix this I needed to
- Obtain the necessary certificate from FastMail. This actually needed to be obtained from DigiCert who are the CA (Certificate Authority).
- Upload the certificate to the handset via Bluetooth.
(1) I could do with a FreeBSD system, (2) I chose to do on my Windows 8.1 laptop with convenient Bluetooth. I could have done both on my old Macbook.
Download the certificate from DiGiCert.
$ wget https://www.digicert.com/CACerts/DigiCertHighAssuranceEVRootCA.crt
Convert it to PEM format.
$ openssl x509 -inform der -in DigiCertHighAssuranceEVRootCA.crt -out DigiCertHighAssuranceEVRootCA.pem
Rename it to a format that is recognised by the K800i filesystem.
$ mv DigiCertHighAssuranceEVRootCA.pem DCHAEVR.crt
Now copy across to the Windows 8.1 machine. I used FileZilla to move everything with sftp. Once on the Windows machine, send DCHAEVR.crt across to the K800i via Bluetooth. I accepted the prompt on the handset to install the DigiCert certificate, then verified installation under Settings->General->Security->Certificates->Trusted certificates.
Finally, send email with no errors!
Many thanks to http://tjworld.net/wiki/SonyEricsson/K800i/InstallDigitalCertificate for details of how to install the actual certificate. I also referred to http://fastmail.wikia.com/wiki/ConfiguringFetchmail for details of the certificate but actually only needed the root certificate.