I think this is a typo in 4.90 RC2, around line 147 s/DEFAILT/DEFAULT/
Patch attached (I hope).
--
Andrew C. Aitchison Cambridge, UK
andrew@???
--- src/configure.default 2017-11-14 19:35:01.000000000 +0000
+++ src/configure.default.new 2017-11-15 15:53:06.485255070 +0000
@@ -154,7 +154,7 @@
# tls_privatekey = /etc/ssl/exim.pem
# For OpenSSL, prefer EC- over RSA-authenticated ciphers
-# tls_require_ciphers = ECDSA:RSA:!COMPLEMENTOFDEFAILT
+# tls_require_ciphers = ECDSA:RSA:!COMPLEMENTOFDEFAULT
# In order to support roaming users who wish to send email from anywhere,
# you may want to make Exim listen on other ports as well as port 25, in
