<a href="https:&#x2F;&#x2F;proxy.jmap.io&#x2F;" rel="nofollow">https:&#x2F;&#x2F;proxy.jmap.io&#x2F;</a> - it contains links to the source code if you&#x27;d like to run it yourself.  It&#x27;s just a few thousand lines of perl, and I wrote it in two groups of about 2 weeks each time (about 6 months apart) - and each time very much part time amongst other things.  It&#x27;s actually not that hard if you already have IMAP, CalDAV and CardDAV client libraries.