Error accessing Kolab Repository

[Gelpi Andrea]

On a Debian 7.7 with Kolab 3.2 installed last june the command

aptitude update

gave this error:

W: A error occurred during the signature verification. The repository is
not updated and the previous index files will be used. GPG error:
http://obs.kolabsys.com ./ Release: The following signatures couldn't be
verified because the public key is not available: NO_PUBKEY 830C2BCF446D5A45

W: Failed to fetch
http://obs.kolabsys.com:82/Kolab:/3.2:/Updates/Debian_7.0/./Release:
W: Some index files failed to download. They have been ignored, or old
ones used instead.


In my /etc/apt/sources.list there is:

# Kolab debian repository
deb http://obs.kolabsys.com:82/Kolab:/3.2/Debian_7.0/ ./
deb http://obs.kolabsys.com:82/Kolab:/3.2:/Updates/Debian_7.0/ ./

I copied this line form docs.kolab.org last june.

Last time I used aptitude was the 30 December 2014.

I've miss something in the last days?

-- 
ing. Andrea Gelpi
***************************************************
La Terra non la abbiamo ereditata dai nostri avi,
ma la abbiamo presa in prestito dai nostri bambini.
***************************************************
We do not inherit the Earth from our parents,
but borrow it from our children.
***************************************************