Relaying on Iphone
Ever since I got the iphone (couple years or so) I have had some emails I cannot reply to because a message comes up that says " cannot send because account or does not support relaying to this account. Its a pain in the ass but at least it leaves it in my drafts. I have a hotmail account which does not seem to have this problem and my business email is on outlook express and it seems to be the one that stops me from relaying. Some days it will give that message when I reply to emails that it previously let me reply to.
Has nothing to do with your iPhone. It's the authentication requirements for your email account.
Let me guess, this is your Shaw/Telus ISP email account? The outgoing mail server hasn't been configured properly. You have to be connected to your ISP's network to be able to send without authentication.
What you need to do is configure the login details the outgoing mail server.