develop a plugin that allows to Digitally Sign an email?

[hamdani]

hi everyone;
I have a project which consist to develop a plugin that allows to sign email using x509 certificate.
I never used Roundcube and I do not not know where to start.
if anyone can help me I will appreciate it.
thanks.

[SKaero]

Take a look at the following documentation:
http://trac.roundcube.net/wiki/Doc_Plugins
http://trac.roundcube.net/wiki/Plugin_Hooks
http://trac.roundcube.net/wiki/Plugin_Events