diff -Naurp SOGo-4.0.2-orig/UI/MailPartViewers/UIxMailPartSignedViewer.m SOGo-4.0.2/UI/MailPartViewers/UIxMailPartSignedViewer.m
--- SOGo-4.0.2-orig/UI/MailPartViewers/UIxMailPartSignedViewer.m	2018-10-10 23:32:06.753085278 -0500
+++ SOGo-4.0.2/UI/MailPartViewers/UIxMailPartSignedViewer.m	2018-10-10 23:33:04.864737333 -0500
@@ -169,10 +169,20 @@
 
       if (err)
         {
+# ifdef HAVE_GNUTLS
           ERR_load_crypto_strings();
           SSL_load_error_strings();
           sslError = ERR_reason_error_string(err);
           validationMessage = [[self labelForKey: [NSString stringWithUTF8String: sslError ? sslError : "(no error information available)"]] retain];
+#elseif (OPENSSL_VERSION_NUMBER < 0x10100000L)
+          ERR_load_crypto_strings();
+          SSL_load_error_strings();
+          sslError = ERR_reason_error_string(err);
+          validationMessage = [[self labelForKey: [NSString stringWithUTF8String: sslError]] retain];
+# else
+          validationMessage = [[self labelForKey: [NSString stringWithUTF8String: sslError]] retain];
+#endif /* HAVE_GNUTLS */
+
         }
     }