I do have my own email server, but it is only for receiving and not for sending; the ISP's SMTP server is used for sending. Probably anyone could do this, if th

I do have my own email server, but it is only for receiving and not for sending; the ISP's SMTP server is used for sending. Probably anyone could do this, if they have a ISP with email (which they ought to have, for this reason). (Also, it seem that in Ubuntu, when installing Exim there is an option to do specifically this.)