Merge branch '5772-sender-ttl' into 'develop'

Remove address_verify_sender_ttl (#5772)

Closes #5772

See merge request ispconfig/ispconfig3!1215

Author: Till Brehm

install/tpl/postfix_2-10.conf.master

@@ -1,5 +1,2 @@
 # Postfix configuration for version 2.10 and up
 smtpd_relay_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination
-
-# This is supported in version 2.9, but lets not create another conf file for it
-address_verify_sender_ttl = 15686s