This week VeriSign issued new intermediate certificates. SSL/TLS certificates issued by VeriSign after Oct 10th 2010 will use a trust chain that includes the new intermediate certificates. You may need to import these certificates into Brightmail to support TLS with partners.
If you use VeriSign for your TLS certificates, I believe you need to import these new intermediate certificates before importing any newly requested VeriSign TLS certificate
See: http://www.verisign.com/support/verisign-intermediate-ca/secure-site-intermediate/index.html for the certificate data