[asterisk-gui] Outbound SIP registrations - the "s" extension

[Yogsi]

Hello,

is it possible to configure user part of the contact header not to be 
the default "s at ipaddress" using Asterisk-GUI when sending REGISTERs?
Usually, this is done in sip.conf as specified in sip.conf.sample (1234 
extension):
register => 2345:password at sip_proxy/1234
;    Register 2345 at sip provider 'sip_proxy'.  Calls from this provider
;    connect to local extension 1234 in extensions.conf
Also,  if no extension is given (1234 in case above), the 's' extension 
is used.

I hope you understand my question.

Regards,
Seb