Originally Posted by
srobarts
Some ISPs won't allow emails to be sent with anything other than their own domain name, others have no restriction providing you are logged on from their connection and the rest will allow you to use other domain names if you request it.
I've read that in many places, but I've never actually come across an ISP that won't let you use any domain name you like, as long as you are connected to them as your ISP and using their SMTP server. I have a wide range of domains for various charitable and "work" purposes, and have never had a problem sending e-mails using any of them. That's been the case with Dircon, Houxou, Pipex, O2, Entanet, BTInternet, PlusNet, and Voda.
Where it can get trickier is when you want to send through ISP2's SMTP while connected to ISP1. That rapidly gets into anti-spam procedures.
My primary ISP (UKFSN) has a "secure SMTP server", and I can use that from anywhere, regardless of where and how I'm connected. It's proved very useful, many times. The only place I don't use it is in Internet cafés and the like.