eSafe Gateway 7.1 Forwarding Proxy with squid

My colleague over at PBSPlaza wrote a nice article about enabling squid on eSafe Gateway 7.1 Forwarding Proxy. Today I had to configure an extra step to enable squid. I followed the instructions from my colleague, but when I tried to start squid I received the following error message.

FATAL: Could not determine fully qualified hostname.  Please set ‘visible_hostname’

Squid Cache (Version 2.6.STABLE18): Terminated abnormally.
CPU Usage: 0.030 seconds = 0.000 user + 0.030 sys
Maximum Resident Size: 0 KB
Page faults with physical i/o: 244
Aborted

I added the following line to /opt/eproxy/etc/squid.conf:

visible_hostname mail.booches.nl

Now squid starts perfectly