This seems to happen on occasion for me as well, including this morning. Give it a few minutes or so and it will likely correct itself. It is possibly a temporary issue with the outgoing mail server.
An email system consists of two servers: IMAP or POP servers (map.telus.net) for incoming mail delivered to your device, and SMTP servers (smtp.telus.net) for outgoing messages. Thus, incoming mail can be unaffected while outgoing is, or vice versa.
Let us know if it continues past an hour, and we can offer further comment and suggestions.
The Telus support person had me change the outgoing server from smtp1.telus.net to smtp.telus.net. I had been using smtp1.telus.net for many months.
And before the Telus person could reply, I also changed the Authentication Method for outgoing emails from "Password-Insecure" to "No authentication".
Once the second part was done, my emails started going successfully.
This is in Thunderbird, but I'm sure the settings are the same in other email clients.
Having the same problem on my iPhone and iPad which were working until 48 hrs ago. Spent over 2 hrs with Telus support and still cannot solve the problem. The only way i can send emails on my iPad is to remove the outgoing smpt fields blank plus use a Telus internet service which is what I have for my home service meaning that I will be unable to use wifi to send emails. As for my iPhone I do not have Telus as my cellular provider which means that I am unable to send emails out for now .
Are all the settings matching the information found here >> http://www.telus.com/en/ab/support/article/set-up-email-iphone-ipad