removing missing exchange server

We're installing a new exchange 2016 server to upgrade a customer from exchange 2010.

Unfortunately the previous company that made the exchange 2010 installation has not correctly dismissed the previous exchange server ( probably 2003 or 2007 ), and the setup ends with the following error 

One or more servers in the existing organization are running Exchange 2000 Server or Exchange Server 2003. Installation can't proceed until all Exchange 2000 or Exchange 2003 servers are removed.
For more information, visit: http://technet.microsoft.com/library(EXCHG.150)/ms.exch.setupreadiness.Exchange2000or2003PresentInOrg.aspx

the get-exchangeserver reports the following

Name Site ServerRole Edition AdminDisplayVersion
---- ---- ---------- ------- -------------------
SERV1 None Standard Version 6.5 (Bui...
EXCHANGE xxx.local/Config... Mailbox,... Standard Version 14.3 (Bu...

the "SERV1" is the one missing to be clean up