diff -urN ../exim-4.89.1.orig/src/tls-openssl.c ./src/tls-openssl.c
--- ../exim-4.89.1.orig/src/tls-openssl.c	2017-11-28 23:40:59.000000000 +0200
+++ ./src/tls-openssl.c	2017-12-05 21:09:51.470270000 +0200
@@ -1525,9 +1525,9 @@
 else
   DEBUG(D_tls) debug_printf("no SSL CTX options to set\n");
 
-/* Disable session cache unconditionally */
-
-(void) SSL_CTX_set_session_cache_mode(*ctxp, SSL_SESS_CACHE_OFF);
+///* Disable session cache unconditionally */
+//
+//(void) SSL_CTX_set_session_cache_mode(*ctxp, SSL_SESS_CACHE_OFF);
 
 /* Initialize with DH parameters if supplied */
 /* Initialize ECDH temp key parameter selection */