The pre-installed email certificates can be viewed at "Settings > Certificates > Email certificates". It is possible to add more certificates using the command line (as the UI support is missing).
In this help article we use the certificate by the name "JSCCinternalCA.crt" as an example. Replace it with the ceritificate you want to add.
For executing the commands below you will need the Developer mode.
1. Copy the certificate file (*.crt) from PC to your Sailfish OS device, to the Home folder "
/home/nemo" first. Use the method of your preference, as suggested in this help article.
2. In your Sailfish device, get the super-user rights first (see the Developer mode article, if needed) and then copy the certificate further to folder "
devel-su ## you will need your SSH password here
cp /home/nemo/JSCCinternalCA.crt /etc/pki/ca-trust/source/anchors
3. Run the command update-ca-trust
4. Open Email certificate from settings and check that added certificate "JCSS internal CA" can be found in the list.
Settings > Certificates > Email certificates
Select that certificate. Restart your device.
5. Turn Developer mode off if you do not need it anymore.