A new fix for the case when ssl_session_cache defined, but ssl is not enabled in any server. The previous r1033 does not help when unused zone becomes used after reconfiguration, so it is backed out. The initial thought was to make SSL modules independed from SSL implementation and to keep OpenSSL code dependance as much as in separate files.

--- a/src/mail/ngx_mail_ssl_module.c
+++ b/src/mail/ngx_mail_ssl_module.c
@@ -474,6 +474,8 @@ ngx_mail_ssl_session_cache(ngx_conf_t *c
         scf->builtin_session_cache = NGX_SSL_NO_BUILTIN_SCACHE;
     }
 
+    scf->shm_zone->init = ngx_ssl_session_cache_init;
+
     return NGX_CONF_OK;
 
 invalid: