Lync/SfB Federation - Certificate trust with another server could not be established

I came across this error while trying to communicate with one of the federated users. Knowing the fact that both parties are openly federated - we were not expecting any issue. But surprisingly, ended with the following error and were not able to communicate or see presence.

1010; reason="Certificate trust with another server could not be established"; ErrorType="The peer certificate is not chained off a trusted root"; TlsTarget="sip.teneo.net"; HRESULT="0x80090325"; source="edge.mydomain.com"; OriginalPresenceState="0"; CurrentPresenceState="0"; MeInsideUser="Yes"; ConversationInitiatedBy="1"; SourceNetwork="5"; RemotePartyCanDoIM="Yes

Logs suggested this as a TLS issue.

The issue is resolved by opening the SIP URL "https://sip.yourdomain.com" in IE on my Lync Servers. It allowed getting a federated partner root certificate from their providers via the automatic root certificate update mechanism.

You will get a page that could not be displayed. However, if your try to communicate with your federated partner, it will be successful.