The certificate used to sign the message was issued by a certificate authority that you do not trust for issuing this kind of certificate.
Chaidh an teisteanas leis an deach an teachdaireachd a shoidhneadh fhoillseachadh le ùghdarras theisteanasan nach eil earbsa agad ann airson foillseachadh a leithid seo de theisteanas.