In reference to www.interspire.smtp.com/support/client-config/live-mail:

Click on the Servers tab. In the field labeled Outgoing mail (SMTP), set the value to the SMTP server name you've been given in the field titled Outgoing mail server (SMTP)

Check the box labeled "My server requires authentication" and then click the button that says Settings.

In the Outgoing Mail Server window, select the radio button labeled "Log on using"
In the field labeled Account name, enter the e-mail address of your registered sender
In the field labeled Password, enter the password

That makes things clearer. As BatBoy has just picked up on as well. Sending is still via SMTP even when using IMAP, and it is those settings you need to address.

In the authentication area there is usually a tick-box for something like "Use the same as incoming". That usually works and is far simpler than doing actual settings.

Edited by RobertoS (Mon 11-Jan-16 12:09:46)

The problem I missed was the incoming being with a different provider. It will need the username and password to be the plusnet account login and password.

Thanks to everyone who replied. I used the "log on using" option and input the username and password of an existing account I have with PN. I managed to get a few emails sent which were received, before it stopped working. Yes, I did click apply after entering the details.

However I have found a different, non PN, smtp server with another provider I have, that works OK.

Once again thank you all for your help.