1. Normal SMTP mail servers only accept your mail if you are
'local' and using their Internet connection. If you use multiple
Internet connections you have to change your settings or get
'Relaying Denied' errors.
2. You may be a mobile user using your laptop or PDA
on-the-move - or you may use two ISP's for better performance or
as a backup - AuthSMTP can be used from almost all ISP's.