I am facing issue while booking Conference room. I am using kolab 16 community installed in 2016 on Debian 8 machine.
Can Any one help me in this regards? Please see below error for your reference.

If you do so, please include this problem report. You can delete your own text from the attached returned message.

The mail system

<resource-confroom-tsb1f4con@tsoft.us>: unknown user:

"resource-confroom-tsb1f4con"