[horde] Kronolith invite mail twice

[Claudio ML]

Hello all,

I have a recent problem with kronolith, version 4.2.9 and Thunderbird
38.2.0 with Lightning 4.0.2.1. When a user make a new event, and invite
someone, the invited person recieve two invites: one from the
Thunderbird Client, and one from the Horde Server.

The strange thing is i have some clients sending only one invite (from
Thunderbird), and others sending 2 invites.

Note: the configuration of thunderbird is the same, also, if i put a
calendar which usually sends two invitation into a clean system, it
sends two invitation. Into the same Client, if i put a calendar which
usually send only one invitation, it sends one. I think is a server
setting, but i don't know where to look. I have also searched for
similar problems on Internet, but found nothing.

Any ideas ?

Claudio.