diff -up dovecot-2.2.36/doc/dovecot-openssl.cnf.bigkey dovecot-2.2.36/doc/dovecot-openssl.cnf
--- dovecot-2.2.36/doc/dovecot-openssl.cnf.bigkey	2017-06-23 13:18:28.000000000 +0200
+++ dovecot-2.2.36/doc/dovecot-openssl.cnf	2018-10-16 17:15:35.836205498 +0200
@@ -1,5 +1,5 @@
 [ req ]
-default_bits = 1024
+default_bits = 3072
 encrypt_key = yes
 distinguished_name = req_dn
 x509_extensions = cert_type