Is there any way to getting work kolab's calendar plugin in roundcube 1.4?

Support
1

**NethServer Version:7.9.2009
Module: webmail 1.4 from stephdl repo

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If you mean kolab groupware calendar plugin I’m Pessimistic this is possible.

Kolab is special;
IIRC it stores everything (not only mails) in IMAP although it can be it uses DAV capacity of their preferred IMAP server cyrus. (NS uses dovecot for IMAP server)