I've successfully changed the settings on both my computer using Outlook 2003, and my wife's using Outlook 2007. (Although there seem to be email "issues" this morning, I don't think they are related to the new settings, as those have been working OK for a few days.)
I'd like to put in screenshots here of the settings I am using on Outlook 2003. (They were basically the same in my wife's Outlook 2007, apart from the slightly different layout of the dialog boxes in that version of the program.) But I can't work out how to get an image into a post here although others seem to be able to do it. So here they are listed.
(1) In the main email account settings screen you need the username to be your email address, and enter your passord, and set the incoming and outgoing servers to be pop3.blueyonder.co.uk and smtp.blueyonder.co.uk.
Then click on "more settings".
In the tab for outgoing server, tick to say that the outgoing server requires authentication, select the option to enter the details yourself (rather than the one that says use the same as the incoming server) and again enter your email address and password. Don't tick the box for using secure password authentication.
Then go on to the Advanced tab. Change the incoming port number to 995 and select encrypted connection. (If I remember right, on OL 2007 there was more than one type on offer and you had to choose SSL from the drop down list. Then choose SSL encryption also for the outgoing server. Then LAST OF ALL set the outgoing port to 465 and click OK. (NB - that order of doing things was important in my experience. If I changed any other setting after changing the outgoing port to 465, I found that it changed itself back to 25 again. So do it last and click OK straight away.)
I hope that helps. Sorry about the lack of screenshots.