diff --git a/smmapdfw/libsmmapdfw/smtp.c b/smmapdfw/libsmmapdfw/smtp.c
index b111ead..8246f0f 100644
--- a/smmapdfw/libsmmapdfw/smtp.c
+++ b/smmapdfw/libsmmapdfw/smtp.c
@@ -231,6 +231,13 @@ int smtp_connect(smtp_t *handle) {
     return -1;
   }
 
+  optval = 0x10; /* TOS=lowdelay*/
+  err = setsockopt(handle->socket, IPPROTO_IP, IP_TOS, (void*)&optval, sizeof(optval));
+  if (-1 == err) {
+    syslog(LOG_DEBUG, "smtp_connect: unable to set IPTOS_LOWDELAY: %d (%s)", errno, strerror(errno));
+    return -1;
+  }
+
   c = fcntl(handle->socket, F_GETFL);
   if (-1 == c) {
     syslog(LOG_DEBUG, "smtp_connect: unable to get flags, errno: %d (%s)", errno, strerror(errno));