Certificate warnings in Cisco Jabber occur when the client cannot validate the identity of the server (e.g., CUCM, IM&P) because the server's security certificate is not trusted. This is typically because the certificate is self-signed or signed by a private Certificate Authority (CA) whose root certificate is not in the client's trust store. The two fundamental ways to resolve this are:
1. Establish trust for the existing certificate: This involves manually installing the server's certificate, or more commonly the root certificate of the CA that issued it, into the local certificate store of the client machine.
2. Use an inherently trusted certificate: This involves replacing the untrusted certificate on the server with one signed by a public, well-known CA that client operating systems trust by default.

B. Reinstall the Jabber client using the /quiet option This option pertains to a silent software installation method and has no impact on certificate trust validation or the underlying security configuration.
C. Configure Jabber with the INVALIDCERTIFICATEBEHAVIOR option set to “RejectAndNotify.” This parameter configures Jabber's reaction to an untrusted certificate. RejectAndNotify is likely the current setting causing the pop-up; it defines the problem's symptom, it is not a solution.
E. Move the user to a different Presence Redundancy Group Presence Redundancy Groups provide high availability for the IM and Presence service. Changing a user's group does not alter the server certificates or resolve the client's trust issue.

1. Cisco

"On-Premises Deployment for Cisco Jabber 14.0

" Security > Certificates.

This guide explicitly states: "For your on-premises deployment

we recommend that you use a public CA to sign your certificates. If you use a private CA

you must ensure that the root certificate for the private CA is in the trust store of all clients." This statement directly supports both correct answers (D and A).

2. Cisco

"Security Guide for Cisco Jabber 12.9

" Certificate Validation.

This document details the certificate validation process. It explains that Jabber uses the underlying operating system's trust store to validate certificates. If the certificate chain cannot be validated up to a trusted root CA in the store

a warning is presented to the user. This underpins the logic for both adding a certificate to the store (A) and using a publicly trusted certificate (D).

3. Cisco

"System Configuration Guide for Cisco Unified Communications Manager

Release 12.5(1) SU1

" Security > Certificate Management.

This guide details the process for managing certificates on the CUCM server. It describes uploading CA-signed certificates to replace the default self-signed certificates to ensure that endpoints like Jabber trust the server without manual intervention on each client. This supports option D as a best practice.