phil has a blog - Config Sendmail

Config Sendmail

The problem was getting “Mailing to remote domains not supported”

The fix turned out to be:

sudo dpkg-reconfigure exim4-config

It had been set to local so was changed to

internet site; mail is sent and received directly using SMTP 

then putting in system name rather than just Ubuntu

System mail name: yourdomain.co.uk

The rest you can just use enter to accept the defaults