This notice concerns only those using Posti’s older OAuth server at oauth.posti.com or oauth.posti.fi. The SSL/TLS certificate for this server is expiring soon, and the certificate authority will change from DigiCert to Telia during the renewal. No changes will be made to oauth2.posti.com.
We will implement the new certificate issued by Telia on Monday, February 2, 2026. This change may cause connectivity issues in some older systems if they do not yet trust Telia’s certificates.
We ask you to take one of the following actions:
Option A (recommended)
Switch to the new address oauth2.posti.com (192.89.57.88), which already uses the certificate issued by Telia. In this case:
Option B
If you continue using the current addresses (oauth.posti.com / oauth.posti.fi), ensure that your system trusts Telia’s certificates before February 2, 2026. Please note, however, that these addresses will eventually be phased out and completely replaced by oauth2.posti.com.
Test environments
If you are using or have previously used the test server oauth.barium.posti.com or oauth.barium.posti.fi, they already use Telia’s certificate. However, we recommend switching to the new test address oauth2.barium.posti.com (192.194.10.32), which uses the same Telia certificate as in production. This corresponds to the actions in Option A (address change, trust Telia, open firewall).
For testing, you can request the creation of a new machine account or a password reset if login is not successful.