I installed stunnel4 (with apt-get) on a new ubuntu server
2013.08.23 16:38:23 LOG7[10589:140529841223424]: SSL alert (read): fatal: unknown CA
2013.08.23 16:38:23 LOG3[10589:140529841223424]: SSL_connect: 14094418: error:14094418:SSL routines:SSL3_READ_BYTES:tlsv1 alert unknown ca
ultimately i copied over pem files from another server and set the group and file ownership to stunnel4