CA open source product

["itsec.info" <itsec.info () gmail com>]

Hi all

For primary usage with an email system I need to setup a certification 
authority.
 
I am interested in flexibility, scalability, and stability beside a well 
written documentation. Furthermore I will use Linux as operating system and 
the product should be open-source.

So far I have briefly checked the following products:
openCA
openXPKI
tinyCA2

Does anybody have any experience which can be shared or are there even other 
open-source products available?

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Any feedback is very much appreciated.
Regards,
Mike