Can't send email with SMTP servers

Many ISPs will not allow off-network access to their SMTP servers. See if Telus has one (AT&T in the US does, and iPhone users can send mail using that server if it's enabled as a secondary server in Settings > Mail, Contacts, Calendars > account > SMTP > Other SMTP Servers).

Glad that helped!

It doesn't work over WiFi because the Telus SMTP server is like the Aliant STMP server, i.e. you can only access it when connected to their network for your internet connection. If you're using WiFi, you're not on Telus' network anymore.

Note that some email account providers allow secure (password) access to their SMTP servers. Gmail and Yahoo are examples - no matter how I'm connected to the internet (cell data, Wi-Fi router at home or at a cafe), I can send mail from my Gmail and Yahoo accounts using their respective SMTP servers.

The only workaround for sending mail over Wi-Fi using your Aliant account would be to know who the ISP is for whatever Wi-Fi network you're on (cable company at someone's house, etc.) and use that SMTP server. Or change mail accounts to something like Gmail or Yahoo.

If the email account provider for the email account is not the internet service provider associated with the wi-fi network your iPhone is connected to at the time and the email account provider for the email account does not have an authenticated SMTP server, you won't be able to send with the account - unless you have access to the ISP's SMTP server being used for your internet connection at the time.

As already provided, most if not all ISPs block the use of SMTP servers that are outside of the ISP's network or that isn't provided by the ISP being used for your internet connection at the time unless the SMTP server is authenticated.

A MobileMe account is my primary email account which has an authenticated SMTP server and I've never had a single problem sending with the account from my iPhone over the last 3 years regardless my internet connection at the time - various wi-fi networks with different associated ISPs or when connected to AT&T's cellular network.

Having an account with an authenticated SMTP server is the key.

I used a MobileMe account as an example. Google provides an authenticated SMTP server with a Gmail account as well for the same reason.

There is much more available with a MobileMe account than email account access. If email account access was all I used it for, I wouldn't have a MobileMe account.