camel Mail changes to only accept lower-cased "cc/bcc" in 2.17

In 2.17 :

The Mail component now requires to configure to, cc, and bcc using lower case keys, eg to=foo@bar.com, instead of To=foo@bar.com as previously.

This causes an issue for the SY camel-mail-binding as we now have to support upper-cased CC/BCC for <2.17 and cc/bcc for >=2.17.